Teach IndVarSimplify how to eliminate remainder operators where the

numerator is an induction variable. For example, with code like this:

  for (i=0;i<n;++i)
    x[i%n] = 0;

IndVarSimplify will now recognize that i is always less than n inside
the loop, and eliminate the remainder.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@101113 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 121 insertions, 0 deletions

diff --git a/test/Transforms/IndVarSimplify/eliminate-rem.ll b/test/Transforms/IndVarSimplify/eliminate-rem.ll
new file mode 100644
index 0000000..f756389
--- /dev/null
+++ b/test/Transforms/IndVarSimplify/eliminate-rem.ll
@@ -0,0 +1,121 @@
+; RUN: opt -indvars -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"
+
+; Indvars should be able to eliminate this srem.
+; CHECK: @simple
+; CHECK-NOT: rem
+; CHECK: ret
+
+define void @simple(i64 %arg, double* %arg3) nounwind {
+bb:
+  %t = icmp slt i64 0, %arg                     ; <i1> [#uses=1]
+  br i1 %t, label %bb4, label %bb12
+
+bb4:                                              ; preds = %bb
+  br label %bb5
+
+bb5:                                              ; preds = %bb4, %bb5
+  %t6 = phi i64 [ %t9, %bb5 ], [ 0, %bb4 ]    ; <i64> [#uses=2]
+  %t7 = srem i64 %t6, %arg                    ; <i64> [#uses=1]
+  %t8 = getelementptr inbounds double* %arg3, i64 %t7 ; <double*> [#uses=1]
+  store double 0.000000e+00, double* %t8
+  %t9 = add nsw i64 %t6, 1                    ; <i64> [#uses=2]
+  %t10 = icmp slt i64 %t9, %arg               ; <i1> [#uses=1]
+  br i1 %t10, label %bb5, label %bb11
+
+bb11:                                             ; preds = %bb5
+  br label %bb12
+
+bb12:                                             ; preds = %bb11, %bb
+  ret void
+}
+
+; Indvars should be able to eliminate the (i+1)%n.
+; CHECK: @f
+; CHECK-NOT: rem
+; CHECK: rem
+; CHECK-NOT: rem
+; CHECK: ret
+
+define i32 @f(i64* %arg, i64 %arg1, i64 %arg2, i64 %arg3) nounwind {
+bb:
+  %t = icmp sgt i64 %arg1, 0                      ; <i1> [#uses=1]
+  br i1 %t, label %bb4, label %bb54
+
+bb4:                                              ; preds = %bb
+  br label %bb5
+
+bb5:                                              ; preds = %bb49, %bb4
+  %t6 = phi i64 [ %t51, %bb49 ], [ 0, %bb4 ]      ; <i64> [#uses=4]
+  %t7 = phi i32 [ %t50, %bb49 ], [ 0, %bb4 ]      ; <i32> [#uses=2]
+  %t8 = add nsw i64 %t6, %arg1                    ; <i64> [#uses=1]
+  %t9 = add nsw i64 %t8, -2                       ; <i64> [#uses=1]
+  %t10 = srem i64 %t9, %arg1                      ; <i64> [#uses=1]
+  %t11 = add nsw i64 %t10, 1                      ; <i64> [#uses=1]
+  %t12 = add nsw i64 %t6, 1                       ; <i64> [#uses=1]
+  %t13 = srem i64 %t12, %arg1                     ; <i64> [#uses=1]
+  %t14 = icmp sgt i64 %arg1, 0                    ; <i1> [#uses=1]
+  br i1 %t14, label %bb15, label %bb49
+
+bb15:                                             ; preds = %bb5
+  br label %bb16
+
+bb16:                                             ; preds = %bb44, %bb15
+  %t17 = phi i64 [ %t46, %bb44 ], [ 0, %bb15 ]    ; <i64> [#uses=1]
+  %t18 = phi i32 [ %t45, %bb44 ], [ %t7, %bb15 ]  ; <i32> [#uses=2]
+  %t19 = icmp sgt i64 %arg1, 0                    ; <i1> [#uses=1]
+  br i1 %t19, label %bb20, label %bb44
+
+bb20:                                             ; preds = %bb16
+  br label %bb21
+
+bb21:                                             ; preds = %bb21, %bb20
+  %t22 = phi i64 [ %t41, %bb21 ], [ 0, %bb20 ]    ; <i64> [#uses=4]
+  %t23 = phi i32 [ %t40, %bb21 ], [ %t18, %bb20 ] ; <i32> [#uses=1]
+  %t24 = mul i64 %t6, %arg1                       ; <i64> [#uses=1]
+  %t25 = mul i64 %t13, %arg1                      ; <i64> [#uses=1]
+  %t26 = add nsw i64 %t24, %t22                   ; <i64> [#uses=1]
+  %t27 = mul i64 %t11, %arg1                      ; <i64> [#uses=1]
+  %t28 = add nsw i64 %t25, %t22                   ; <i64> [#uses=1]
+  %t29 = getelementptr inbounds i64* %arg, i64 %t26 ; <i64*> [#uses=1]
+  %t30 = add nsw i64 %t27, %t22                   ; <i64> [#uses=1]
+  %t31 = getelementptr inbounds i64* %arg, i64 %t28 ; <i64*> [#uses=1]
+  %t32 = zext i32 %t23 to i64                     ; <i64> [#uses=1]
+  %t33 = load i64* %t29                           ; <i64> [#uses=1]
+  %t34 = getelementptr inbounds i64* %arg, i64 %t30 ; <i64*> [#uses=1]
+  %t35 = load i64* %t31                           ; <i64> [#uses=1]
+  %t36 = add nsw i64 %t32, %t33                   ; <i64> [#uses=1]
+  %t37 = add nsw i64 %t36, %t35                   ; <i64> [#uses=1]
+  %t38 = load i64* %t34                           ; <i64> [#uses=1]
+  %t39 = add nsw i64 %t37, %t38                   ; <i64> [#uses=1]
+  %t40 = trunc i64 %t39 to i32                    ; <i32> [#uses=2]
+  %t41 = add nsw i64 %t22, 1                      ; <i64> [#uses=2]
+  %t42 = icmp slt i64 %t41, %arg1                 ; <i1> [#uses=1]
+  br i1 %t42, label %bb21, label %bb43
+
+bb43:                                             ; preds = %bb21
+  br label %bb44
+
+bb44:                                             ; preds = %bb43, %bb16
+  %t45 = phi i32 [ %t18, %bb16 ], [ %t40, %bb43 ] ; <i32> [#uses=2]
+  %t46 = add nsw i64 %t17, 1                      ; <i64> [#uses=2]
+  %t47 = icmp slt i64 %t46, %arg1                 ; <i1> [#uses=1]
+  br i1 %t47, label %bb16, label %bb48
+
+bb48:                                             ; preds = %bb44
+  br label %bb49
+
+bb49:                                             ; preds = %bb48, %bb5
+  %t50 = phi i32 [ %t7, %bb5 ], [ %t45, %bb48 ]   ; <i32> [#uses=2]
+  %t51 = add nsw i64 %t6, 1                       ; <i64> [#uses=2]
+  %t52 = icmp slt i64 %t51, %arg1                 ; <i1> [#uses=1]
+  br i1 %t52, label %bb5, label %bb53
+
+bb53:                                             ; preds = %bb49
+  br label %bb54
+
+bb54:                                             ; preds = %bb53, %bb
+  %t55 = phi i32 [ 0, %bb ], [ %t50, %bb53 ]      ; <i32> [#uses=1]
+  ret i32 %t55
+}