DAGCombiner: Allow the DAGCombiner to combine multiple FDIVs with the same divisor info FMULs by the reciprocal.

E.g., ( a / D; b / D ) -> ( recip = 1.0 / D; a * recip; b * recip)

A hook is added to allow the target to control whether it needs to do such combine.

Reviewed in http://reviews.llvm.org/D6334

llvm-svn: 222510

1 files changed, 94 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/AArch64/fdiv-combine.ll b/llvm/test/CodeGen/AArch64/fdiv-combine.ll
new file mode 100644
index 00000000000..389eefd97b2
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/fdiv-combine.ll
@@ -0,0 +1,94 @@
+; RUN: llc -march=aarch64 < %s | FileCheck %s
+
+; Following test cases check:
+;   a / D; b / D; c / D;
+;                =>
+;   recip = 1.0 / D; a * recip; b * recip; c * recip;
+define void @three_fdiv_float(float %D, float %a, float %b, float %c) #0 {
+; CHECK-LABEL: three_fdiv_float:
+; CHECK: fdiv
+; CHECK-NEXT-NOT: fdiv
+; CHECK: fmul
+; CHECK: fmul
+; CHECK: fmul
+  %div = fdiv float %a, %D
+  %div1 = fdiv float %b, %D
+  %div2 = fdiv float %c, %D
+  tail call void @foo_3f(float %div, float %div1, float %div2)
+  ret void
+}
+
+define void @three_fdiv_double(double %D, double %a, double %b, double %c) #0 {
+; CHECK-LABEL: three_fdiv_double:
+; CHECK: fdiv
+; CHECK-NEXT-NOT: fdiv
+; CHECK: fmul
+; CHECK: fmul
+; CHECK: fmul
+  %div = fdiv double %a, %D
+  %div1 = fdiv double %b, %D
+  %div2 = fdiv double %c, %D
+  tail call void @foo_3d(double %div, double %div1, double %div2)
+  ret void
+}
+
+define void @three_fdiv_4xfloat(<4 x float> %D, <4 x float> %a, <4 x float> %b, <4 x float> %c) #0 {
+; CHECK-LABEL: three_fdiv_4xfloat:
+; CHECK: fdiv
+; CHECK-NEXT-NOT: fdiv
+; CHECK: fmul
+; CHECK: fmul
+; CHECK: fmul
+  %div = fdiv <4 x float> %a, %D
+  %div1 = fdiv <4 x float> %b, %D
+  %div2 = fdiv <4 x float> %c, %D
+  tail call void @foo_3_4xf(<4 x float> %div, <4 x float> %div1, <4 x float> %div2)
+  ret void
+}
+
+define void @three_fdiv_2xdouble(<2 x double> %D, <2 x double> %a, <2 x double> %b, <2 x double> %c) #0 {
+; CHECK-LABEL: three_fdiv_2xdouble:
+; CHECK: fdiv
+; CHECK-NEXT-NOT: fdiv
+; CHECK: fmul
+; CHECK: fmul
+; CHECK: fmul
+  %div = fdiv <2 x double> %a, %D
+  %div1 = fdiv <2 x double> %b, %D
+  %div2 = fdiv <2 x double> %c, %D
+  tail call void @foo_3_2xd(<2 x double> %div, <2 x double> %div1, <2 x double> %div2)
+  ret void
+}
+
+; Following test cases check we never combine two FDIVs if neither of them
+; calculates a reciprocal.
+define void @two_fdiv_float(float %D, float %a, float %b) #0 {
+; CHECK-LABEL: two_fdiv_float:
+; CHECK: fdiv
+; CHECK: fdiv
+; CHECK-NEXT-NOT: fmul
+  %div = fdiv float %a, %D
+  %div1 = fdiv float %b, %D
+  tail call void @foo_2f(float %div, float %div1)
+  ret void
+}
+
+define void @two_fdiv_double(double %D, double %a, double %b) #0 {
+; CHECK-LABEL: two_fdiv_double:
+; CHECK: fdiv
+; CHECK: fdiv
+; CHECK-NEXT-NOT: fmul
+  %div = fdiv double %a, %D
+  %div1 = fdiv double %b, %D
+  tail call void @foo_2d(double %div, double %div1)
+  ret void
+}
+
+declare void @foo_3f(float, float, float)
+declare void @foo_3d(double, double, double)
+declare void @foo_3_4xf(<4 x float>, <4 x float>, <4 x float>)
+declare void @foo_3_2xd(<2 x double>, <2 x double>, <2 x double>)
+declare void @foo_2f(float, float)
+declare void @foo_2d(double, double)
+
+attributes #0 = { "unsafe-fp-math"="true" }