Enable machine sinking critical edge splitting. e.g.

define double @foo(double %x, double %y, i1 %c) nounwind {
  %a = fdiv double %x, 3.2
  %z = select i1 %c, double %a, double %y
  ret double %z
}

Was:
_foo:
        divsd   LCPI0_0(%rip), %xmm0
        testb   $1, %dil
        jne     LBB0_2
        movaps  %xmm1, %xmm0
LBB0_2:
        ret

Now:
_foo:
        testb   $1, %dil
        je      LBB0_2
        divsd   LCPI0_0(%rip), %xmm0
        ret
LBB0_2:
        movaps  %xmm1, %xmm0
        ret

This avoids the divsd when early exit is taken.
rdar://8454886


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@114372 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 24 insertions, 5 deletions

diff --git a/test/CodeGen/X86/sink-hoist.ll b/test/CodeGen/X86/sink-hoist.ll
index acba528..31f41ee 100644
--- a/test/CodeGen/X86/sink-hoist.ll
+++ b/test/CodeGen/X86/sink-hoist.ll
@@ -6,10 +6,11 @@
 ; that it's conditionally evaluated.
 
 ; CHECK: foo:
-; CHECK:      divsd
 ; CHECK-NEXT: testb $1, %dil
-; CHECK-NEXT: jne
+; CHECK-NEXT: je
 ; CHECK-NEXT: divsd
+; CHECK-NEXT: ret
+; CHECK:      divsd
 
 define double @foo(double %x, double %y, i1 %c) nounwind {
   %a = fdiv double %x, 3.2
@@ -18,6 +19,24 @@ define double @foo(double %x, double %y, i1 %c) nounwind {
   ret double %z
 }
 
+; Make sure the critical edge is broken so the divsd is sunken below
+; the conditional branch.
+; rdar://8454886
+
+; CHECK: split:
+; CHECK-NEXT: testb $1, %dil
+; CHECK-NEXT: je
+; CHECK-NEXT: divsd
+; CHECK-NEXT: ret
+; CHECK:      movaps
+; CHECK-NEXT: ret
+define double @split(double %x, double %y, i1 %c) nounwind {
+  %a = fdiv double %x, 3.2
+  %z = select i1 %c, double %a, double %y
+  ret double %z
+}
+
+
 ; Hoist floating-point constant-pool loads out of loops.
 
 ; CHECK: bar:
@@ -68,9 +87,9 @@ return:
 ; Codegen should hoist and CSE these constants.
 
 ; CHECK: vv:
-; CHECK: LCPI2_0(%rip), %xmm0
-; CHECK: LCPI2_1(%rip), %xmm1
-; CHECK: LCPI2_2(%rip), %xmm2
+; CHECK: LCPI3_0(%rip), %xmm0
+; CHECK: LCPI3_1(%rip), %xmm1
+; CHECK: LCPI3_2(%rip), %xmm2
 ; CHECK: align
 ; CHECK-NOT: LCPI
 ; CHECK: ret