GVN proceeds in the presence of dead code.

This is how it ignores the dead code:
1) When a dead branch target, say block B, is identified, all the
    blocks dominated by B is dead as well.

2) The PHIs of those blocks in dominance-frontier(B) is updated such
   that the operands corresponding to dead predecessors are replaced
   by "UndefVal".

   Using lattice's jargon, the "UndefVal" is the "Top" in essence.
   Phi node like this "phi(v1 bb1, undef xx)" will be optimized into
   "v1" if v1 is constant, or v1 is an instruction which dominate this
   PHI node.

3) When analyzing the availability of a load L, all dead mem-ops which
   L depends on disguise as a load which evaluate exactly same value as L.

4) The dead mem-ops will be materialized as "UndefVal" during code motion.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191017 91177308-0d34-0410-b5e6-96231b3b80d8

8 files changed, 220 insertions, 22 deletions

diff --git a/test/Transforms/GVN/2007-07-26-InterlockingLoops.ll b/test/Transforms/GVN/2007-07-26-InterlockingLoops.ll
index a1cc008..5a15f0e 100644
--- a/test/Transforms/GVN/2007-07-26-InterlockingLoops.ll
+++ b/test/Transforms/GVN/2007-07-26-InterlockingLoops.ll
@@ -2,7 +2,7 @@
 
 @last = external global [65 x i32*]
 
-define i32 @NextRootMove(i32 %wtm) {
+define i32 @NextRootMove(i32 %wtm, i32 %x, i32 %y, i32 %z) {
 entry:
         %A = alloca i32*
 	%tmp17618 = load i32** getelementptr ([65 x i32*]* @last, i32 0, i32 1), align 4
@@ -15,12 +15,14 @@ entry:
 	br label %cond_true116
 
 cond_true116:
-	br i1 false, label %cond_true128, label %cond_true145
+   %cmp = icmp eq i32 %x, %y
+	br i1 %cmp, label %cond_true128, label %cond_true145
 
 cond_true128:
 	%tmp17625 = load i32** getelementptr ([65 x i32*]* @last, i32 0, i32 1), align 4
         store i32* %tmp17625, i32** %A
-	br i1 false, label %bb98.backedge, label %return.loopexit
+   %cmp1 = icmp eq i32 %x, %z
+	br i1 %cmp1 , label %bb98.backedge, label %return.loopexit
 
 bb98.backedge:
 	br label %cond_true116
diff --git a/test/Transforms/GVN/2008-07-02-Unreachable.ll b/test/Transforms/GVN/2008-07-02-Unreachable.ll
index 4f07868..ce83fa4 100644
--- a/test/Transforms/GVN/2008-07-02-Unreachable.ll
+++ b/test/Transforms/GVN/2008-07-02-Unreachable.ll
@@ -3,10 +3,11 @@
 
 @g_3 = external global i8		; <i8*> [#uses=2]
 
-define i8 @func_1() nounwind  {
+define i8 @func_1(i32 %x, i32 %y) nounwind  {
 entry:
   %A = alloca i8
-	br i1 false, label %ifelse, label %ifthen
+    %cmp = icmp eq i32 %x, %y
+	br i1 %cmp, label %ifelse, label %ifthen
 
 ifthen:		; preds = %entry
 	br label %ifend
@@ -14,9 +15,6 @@ ifthen:		; preds = %entry
 ifelse:		; preds = %entry
 	%tmp3 = load i8* @g_3		; <i8> [#uses=0]
         store i8 %tmp3, i8* %A
-	br label %forcond.thread
-
-forcond.thread:		; preds = %ifelse
 	br label %afterfor
 
 forcond:		; preds = %forinc
diff --git a/test/Transforms/GVN/cond_br.ll b/test/Transforms/GVN/cond_br.ll
new file mode 100644
index 0000000..918e7d4
--- /dev/null
+++ b/test/Transforms/GVN/cond_br.ll
@@ -0,0 +1,55 @@
+; RUN: opt -basicaa -gvn -S < %s | FileCheck %s
+@y = external global i32
+@z = external global i32
+
+; Function Attrs: nounwind ssp uwtable
+define void @foo(i32 %x) {
+; CHECK: @foo(i32 %x)
+; CHECK: %.pre = load i32* @y
+; CHECK: call void @bar(i32 %.pre)
+
+  %t = sub i32 %x, %x
+  %.pre = load i32* @y, align 4
+  %cmp = icmp sgt i32 %t, 2
+  br i1 %cmp, label %if.then, label %entry.if.end_crit_edge
+
+entry.if.end_crit_edge:                           ; preds = %entry
+  br label %if.end
+
+if.then:                                          ; preds = %entry
+  %add = add nsw i32 %x, 3
+  store i32 %add, i32* @y, align 4
+  br label %if.end
+
+if.end:                                           ; preds = %entry.if.end_crit_edge, %if.then
+  %1 = phi i32 [ %.pre, %entry.if.end_crit_edge ], [ %add, %if.then ]
+  tail call void @bar(i32 %1)
+  ret void
+}
+
+define void @foo2(i32 %x) {
+; CHECK: @foo2(i32 %x)
+; CHECK: %.pre = load i32* @y
+; CHECK: tail call void @bar(i32 %.pre)
+entry:
+  %t = sub i32 %x, %x
+  %.pre = load i32* @y, align 4
+  %cmp = icmp sgt i32 %t, 2
+  br i1 %cmp, label %if.then, label %if.else
+
+if.then:                                          ; preds = %entry
+  %add = add nsw i32 %x, 3
+  store i32 %add, i32* @y, align 4
+  br label %if.end
+
+if.else:                                          ; preds = %entry
+  store i32 1, i32* @z, align 4
+  br label %if.end
+
+if.end:                                           ; preds = %if.else, %if.then
+  %0 = phi i32 [ %.pre, %if.else ], [ %add, %if.then ]
+  tail call void @bar(i32 %0)
+  ret void
+}
+
+declare void @bar(i32)
diff --git a/test/Transforms/GVN/cond_br2.ll b/test/Transforms/GVN/cond_br2.ll
new file mode 100644
index 0000000..e0ef39d
--- /dev/null
+++ b/test/Transforms/GVN/cond_br2.ll
@@ -0,0 +1,139 @@
+; RUN: opt -basicaa -gvn -S < %s | FileCheck %s
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+
+%"class.llvm::SmallVector" = type { %"class.llvm::SmallVectorImpl", [1 x %"union.llvm::SmallVectorBase::U"] }
+%"class.llvm::SmallVectorImpl" = type { %"class.llvm::SmallVectorTemplateBase" }
+%"class.llvm::SmallVectorTemplateBase" = type { %"class.llvm::SmallVectorTemplateCommon" }
+%"class.llvm::SmallVectorTemplateCommon" = type { %"class.llvm::SmallVectorBase" }
+%"class.llvm::SmallVectorBase" = type { i8*, i8*, i8*, %"union.llvm::SmallVectorBase::U" }
+%"union.llvm::SmallVectorBase::U" = type { x86_fp80 }
+
+; Function Attrs: ssp uwtable
+define void @_Z4testv() #0 {
+; CHECK: @_Z4testv()
+; CHECK: invoke.cont:
+; CHECK: br i1 true, label %new.notnull.i11, label %if.end.i14
+; CHECK: Retry.i10:
+
+entry:
+  %sv = alloca %"class.llvm::SmallVector", align 16
+  %0 = bitcast %"class.llvm::SmallVector"* %sv to i8*
+  call void @llvm.lifetime.start(i64 64, i8* %0) #1
+  %BeginX.i.i.i.i.i.i = getelementptr inbounds %"class.llvm::SmallVector"* %sv, i64 0, i32 0, i32 0, i32 0, i32 0, i32 0
+  %FirstEl.i.i.i.i.i.i = getelementptr inbounds %"class.llvm::SmallVector"* %sv, i64 0, i32 0, i32 0, i32 0, i32 0, i32 3
+  %1 = bitcast %"union.llvm::SmallVectorBase::U"* %FirstEl.i.i.i.i.i.i to i8*
+  store i8* %1, i8** %BeginX.i.i.i.i.i.i, align 16, !tbaa !0
+  %EndX.i.i.i.i.i.i = getelementptr inbounds %"class.llvm::SmallVector"* %sv, i64 0, i32 0, i32 0, i32 0, i32 0, i32 1
+  store i8* %1, i8** %EndX.i.i.i.i.i.i, align 8, !tbaa !0
+  %CapacityX.i.i.i.i.i.i = getelementptr inbounds %"class.llvm::SmallVector"* %sv, i64 0, i32 0, i32 0, i32 0, i32 0, i32 2
+  %add.ptr.i.i.i.i2.i.i = getelementptr inbounds %"union.llvm::SmallVectorBase::U"* %FirstEl.i.i.i.i.i.i, i64 2
+  %add.ptr.i.i.i.i.i.i = bitcast %"union.llvm::SmallVectorBase::U"* %add.ptr.i.i.i.i2.i.i to i8*
+  store i8* %add.ptr.i.i.i.i.i.i, i8** %CapacityX.i.i.i.i.i.i, align 16, !tbaa !0
+  %EndX.i = getelementptr inbounds %"class.llvm::SmallVector"* %sv, i64 0, i32 0, i32 0, i32 0, i32 0, i32 1
+  %2 = load i8** %EndX.i, align 8, !tbaa !0
+  %CapacityX.i = getelementptr inbounds %"class.llvm::SmallVector"* %sv, i64 0, i32 0, i32 0, i32 0, i32 0, i32 2
+  %cmp.i = icmp ult i8* %2, %add.ptr.i.i.i.i.i.i
+  br i1 %cmp.i, label %Retry.i, label %if.end.i
+
+Retry.i:                                          ; preds = %.noexc, %entry
+  %3 = phi i8* [ %2, %entry ], [ %.pre.i, %.noexc ]
+  %new.isnull.i = icmp eq i8* %3, null
+  br i1 %new.isnull.i, label %invoke.cont, label %new.notnull.i
+
+new.notnull.i:                                    ; preds = %Retry.i
+  %4 = bitcast i8* %3 to i32*
+  store i32 1, i32* %4, align 4, !tbaa !3
+  br label %invoke.cont
+
+if.end.i:                                         ; preds = %entry
+  %5 = getelementptr inbounds %"class.llvm::SmallVector"* %sv, i64 0, i32 0, i32 0, i32 0, i32 0
+  invoke void @_ZN4llvm15SmallVectorBase8grow_podEmm(%"class.llvm::SmallVectorBase"* %5, i64 0, i64 4)
+          to label %.noexc unwind label %lpad
+
+.noexc:                                           ; preds = %if.end.i
+  %.pre.i = load i8** %EndX.i, align 8, !tbaa !0
+  br label %Retry.i
+
+invoke.cont:                                      ; preds = %new.notnull.i, %Retry.i
+  %add.ptr.i = getelementptr inbounds i8* %3, i64 4
+  store i8* %add.ptr.i, i8** %EndX.i, align 8, !tbaa !0
+  %6 = load i8** %CapacityX.i, align 16, !tbaa !0
+  %cmp.i8 = icmp ult i8* %add.ptr.i, %6
+  br i1 %cmp.i8, label %new.notnull.i11, label %if.end.i14
+
+Retry.i10:                                        ; preds = %if.end.i14
+  %.pre.i13 = load i8** %EndX.i, align 8, !tbaa !0
+  %new.isnull.i9 = icmp eq i8* %.pre.i13, null
+  br i1 %new.isnull.i9, label %invoke.cont2, label %new.notnull.i11
+
+new.notnull.i11:                                  ; preds = %invoke.cont, %Retry.i10
+  %7 = phi i8* [ %.pre.i13, %Retry.i10 ], [ %add.ptr.i, %invoke.cont ]
+  %8 = bitcast i8* %7 to i32*
+  store i32 2, i32* %8, align 4, !tbaa !3
+  br label %invoke.cont2
+
+if.end.i14:                                       ; preds = %invoke.cont
+  %9 = getelementptr inbounds %"class.llvm::SmallVector"* %sv, i64 0, i32 0, i32 0, i32 0, i32 0
+  invoke void @_ZN4llvm15SmallVectorBase8grow_podEmm(%"class.llvm::SmallVectorBase"* %9, i64 0, i64 4)
+          to label %Retry.i10 unwind label %lpad
+
+invoke.cont2:                                     ; preds = %new.notnull.i11, %Retry.i10
+  %10 = phi i8* [ null, %Retry.i10 ], [ %7, %new.notnull.i11 ]
+  %add.ptr.i12 = getelementptr inbounds i8* %10, i64 4
+  store i8* %add.ptr.i12, i8** %EndX.i, align 8, !tbaa !0
+  invoke void @_Z1gRN4llvm11SmallVectorIiLj8EEE(%"class.llvm::SmallVector"* %sv)
+          to label %invoke.cont3 unwind label %lpad
+
+invoke.cont3:                                     ; preds = %invoke.cont2
+  %11 = load i8** %BeginX.i.i.i.i.i.i, align 16, !tbaa !0
+  %cmp.i.i.i.i19 = icmp eq i8* %11, %1
+  br i1 %cmp.i.i.i.i19, label %_ZN4llvm11SmallVectorIiLj8EED1Ev.exit21, label %if.then.i.i.i20
+
+if.then.i.i.i20:                                  ; preds = %invoke.cont3
+  call void @free(i8* %11) #1
+  br label %_ZN4llvm11SmallVectorIiLj8EED1Ev.exit21
+
+_ZN4llvm11SmallVectorIiLj8EED1Ev.exit21:          ; preds = %invoke.cont3, %if.then.i.i.i20
+  call void @llvm.lifetime.end(i64 64, i8* %0) #1
+  ret void
+
+lpad:                                             ; preds = %if.end.i14, %if.end.i, %invoke.cont2
+  %12 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          cleanup
+  %13 = load i8** %BeginX.i.i.i.i.i.i, align 16, !tbaa !0
+  %cmp.i.i.i.i = icmp eq i8* %13, %1
+  br i1 %cmp.i.i.i.i, label %eh.resume, label %if.then.i.i.i
+
+if.then.i.i.i:                                    ; preds = %lpad
+  call void @free(i8* %13) #1
+  br label %eh.resume
+
+eh.resume:                                        ; preds = %if.then.i.i.i, %lpad
+  resume { i8*, i32 } %12
+}
+
+; Function Attrs: nounwind
+declare void @llvm.lifetime.start(i64, i8* nocapture) #1
+
+declare i32 @__gxx_personality_v0(...)
+
+declare void @_Z1gRN4llvm11SmallVectorIiLj8EEE(%"class.llvm::SmallVector"*) #2
+
+; Function Attrs: nounwind
+declare void @llvm.lifetime.end(i64, i8* nocapture) #1
+
+declare void @_ZN4llvm15SmallVectorBase8grow_podEmm(%"class.llvm::SmallVectorBase"*, i64, i64) #2
+
+; Function Attrs: nounwind
+declare void @free(i8* nocapture) #3
+
+attributes #0 = { ssp uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind }
+attributes #2 = { "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #3 = { nounwind "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!0 = metadata !{metadata !"any pointer", metadata !1}
+!1 = metadata !{metadata !"omnipotent char", metadata !2}
+!2 = metadata !{metadata !"Simple C/C++ TBAA"}
+!3 = metadata !{metadata !"int", metadata !1}
+
diff --git a/test/Transforms/GVN/local-pre.ll b/test/Transforms/GVN/local-pre.ll
index 1d0dadf..2c92699 100644
--- a/test/Transforms/GVN/local-pre.ll
+++ b/test/Transforms/GVN/local-pre.ll
@@ -1,9 +1,9 @@
 ; RUN: opt < %s -gvn -enable-pre -S | grep "b.pre"
 
-define i32 @main(i32 %p) {
+define i32 @main(i32 %p, i32 %q) {
 block1:
-  
-	br i1 true, label %block2, label %block3
+    %cmp = icmp eq i32 %p, %q 
+	br i1 %cmp, label %block2, label %block3
 
 block2:
  %a = add i32 %p, 1
diff --git a/test/Transforms/GVN/rle-nonlocal.ll b/test/Transforms/GVN/rle-nonlocal.ll
index 6b74e9a..8229aaa 100644
--- a/test/Transforms/GVN/rle-nonlocal.ll
+++ b/test/Transforms/GVN/rle-nonlocal.ll
@@ -1,8 +1,9 @@
 ; RUN: opt < %s -basicaa -gvn -S | FileCheck %s
 
-define i32 @main(i32** %p) {
+define i32 @main(i32** %p, i32 %x, i32 %y) {
 block1:
-	br i1 true, label %block2, label %block3
+    %cmp = icmp eq i32 %x, %y
+	br i1 %cmp , label %block2, label %block3
 
 block2:
  %a = load i32** %p
diff --git a/test/Transforms/GVN/rle-semidominated.ll b/test/Transforms/GVN/rle-semidominated.ll
index 71aa548..923cd03 100644
--- a/test/Transforms/GVN/rle-semidominated.ll
+++ b/test/Transforms/GVN/rle-semidominated.ll
@@ -1,9 +1,10 @@
 ; RUN: opt < %s -basicaa -gvn -S | grep "DEAD = phi i32 "
 
-define i32 @main(i32* %p) {
+define i32 @main(i32* %p, i32 %x, i32 %y) {
 block1:
   %z = load i32* %p
-	br i1 true, label %block2, label %block3
+  %cmp = icmp eq i32 %x, %y
+	br i1 %cmp, label %block2, label %block3
 
 block2:
  br label %block4
diff --git a/test/Transforms/GVN/rle.ll b/test/Transforms/GVN/rle.ll
index 8787dd5..a928a16 100644
--- a/test/Transforms/GVN/rle.ll
+++ b/test/Transforms/GVN/rle.ll
@@ -357,13 +357,14 @@ Cont:
 ; CHECK: ret i8 %A
 }
 
-define i32 @chained_load(i32** %p) {
+define i32 @chained_load(i32** %p, i32 %x, i32 %y) {
 block1:
   %A = alloca i32*
 
   %z = load i32** %p
   store i32* %z, i32** %A
-  br i1 true, label %block2, label %block3
+  %cmp = icmp eq i32 %x, %y
+  br i1 %cmp, label %block2, label %block3
 
 block2:
  %a = load i32** %p
@@ -427,10 +428,11 @@ TY:
   ret i32 0
 }
 
-define i32 @phi_trans3(i32* %p) {
+define i32 @phi_trans3(i32* %p, i32 %x, i32 %y, i32 %z) {
 ; CHECK-LABEL: @phi_trans3(
 block1:
-  br i1 true, label %block2, label %block3
+  %cmpxy = icmp eq i32 %x, %y
+  br i1 %cmpxy, label %block2, label %block3
 
 block2:
  store i32 87, i32* %p
@@ -443,7 +445,7 @@ block3:
 
 block4:
   %A = phi i32 [-1, %block2], [42, %block3]
-  br i1 true, label %block5, label %exit
+  br i1 %cmpxy, label %block5, label %exit
   
 ; CHECK: block4:
 ; CHECK-NEXT: %D = phi i32 [ 87, %block2 ], [ 97, %block3 ]  
@@ -451,11 +453,11 @@ block4:
 
 block5:
   %B = add i32 %A, 1
-  br i1 true, label %block6, label %exit
+  br i1 %cmpxy, label %block6, label %exit
   
 block6:
   %C = getelementptr i32* %p, i32 %B
-  br i1 true, label %block7, label %exit
+  br i1 %cmpxy, label %block7, label %exit
   
 block7:
   %D = load i32* %C