[Reassociation] Add support for reassociation with unsafe algebra.

Vector instructions are (still) not supported for either integer or floating
point.  Hopefully, that work will be landed shortly.

llvm-svn: 215647

1 files changed, 32 insertions, 0 deletions

diff --git a/llvm/test/Transforms/Reassociate/fast-multistep.ll b/llvm/test/Transforms/Reassociate/fast-multistep.ll
new file mode 100644
index 00000000000..45e15c7f353
--- /dev/null
+++ b/llvm/test/Transforms/Reassociate/fast-multistep.ll
@@ -0,0 +1,32 @@
+; RUN: opt < %s -reassociate -S | FileCheck %s
+
+define float @fmultistep1(float %a, float %b, float %c) {
+; Check that a*a*b+a*a*c is turned into a*(a*(b+c)).
+; CHECK-LABEL: @fmultistep1
+; CHECK-NEXT: fadd fast float %c, %b
+; CHECK-NEXT: fmul fast float %a, %tmp2
+; CHECK-NEXT: fmul fast float %tmp3, %a
+; CHECK-NEXT: ret float
+
+  %t0 = fmul fast float %a, %b
+  %t1 = fmul fast float %a, %t0 ; a*(a*b)
+  %t2 = fmul fast float %a, %c
+  %t3 = fmul fast float %a, %t2 ; a*(a*c)
+  %t4 = fadd fast float %t1, %t3
+  ret float %t4
+}
+
+define float @fmultistep2(float %a, float %b, float %c, float %d) {
+; Check that a*b+a*c+d is turned into a*(b+c)+d.
+; CHECK-LABEL: @fmultistep2
+; CHECK-NEXT: fadd fast float %c, %b
+; CHECK-NEXT: fmul fast float %tmp, %a
+; CHECK-NEXT: fadd fast float %tmp1, %d
+; CHECK-NEXT: ret float
+
+  %t0 = fmul fast float %a, %b
+  %t1 = fmul fast float %a, %c
+  %t2 = fadd fast float %t1, %d ; a*c+d
+  %t3 = fadd fast float %t0, %t2 ; a*b+(a*c+d)
+  ret float %t3
+}