From 90f4c8ec299a19ec4c78166865e96c382cb32f92 Mon Sep 17 00:00:00 2001
From: Sanjay Patel <spatel@rotateright.com>
Date: Tue, 20 Feb 2018 16:08:15 +0000
Subject: [InstCombine] fold fdiv with non-splat divisor to fmul: X/C --> X *
 (1/C)

llvm-svn: 325590
---
 llvm/test/Transforms/InstCombine/fast-math.ll |  7 ++++++-
 llvm/test/Transforms/InstCombine/fdiv.ll      | 13 ++++++++++---
 2 files changed, 16 insertions(+), 4 deletions(-)

(limited to 'llvm/test/Transforms')

diff --git a/llvm/test/Transforms/InstCombine/fast-math.ll b/llvm/test/Transforms/InstCombine/fast-math.ll
index 4a0244561e0..1843a784ab8 100644
--- a/llvm/test/Transforms/InstCombine/fast-math.ll
+++ b/llvm/test/Transforms/InstCombine/fast-math.ll
@@ -229,6 +229,9 @@ define float @fmul_distribute1(float %f1) {
 }
 
 ; (X/C1 + C2) * C3 => X/(C1/C3) + C2*C3
+; TODO: We don't convert the fast fdiv to fmul because that would be multiplication
+; by a denormal, but we could do better when we know that denormals are not a problem.
+
 define double @fmul_distribute2(double %f1, double %f2) {
 ; CHECK-LABEL: @fmul_distribute2(
 ; CHECK-NEXT:    [[TMP1:%.*]] = fdiv fast double [[F1:%.*]], 0x7FE8000000000000
@@ -345,7 +348,9 @@ define float @fmul4(float %f1, float %f2) {
 
 ; X / C1 * C2 => X / (C2/C1) if  C1/C2 is either a special value of a denormal,
 ;  and C2/C1 is a normal value.
-;
+; TODO: We don't convert the fast fdiv to fmul because that would be multiplication
+; by a denormal, but we could do better when we know that denormals are not a problem.
+
 define float @fmul5(float %f1, float %f2) {
 ; CHECK-LABEL: @fmul5(
 ; CHECK-NEXT:    [[TMP1:%.*]] = fdiv fast float [[F1:%.*]], 0x47E8000000000000
diff --git a/llvm/test/Transforms/InstCombine/fdiv.ll b/llvm/test/Transforms/InstCombine/fdiv.ll
index 90fea3baf1e..3a2c62c5071 100644
--- a/llvm/test/Transforms/InstCombine/fdiv.ll
+++ b/llvm/test/Transforms/InstCombine/fdiv.ll
@@ -86,11 +86,9 @@ define <2 x float> @not_exact_but_allow_recip_splat(<2 x float> %x) {
   ret <2 x float> %div
 }
 
-; FIXME: Vector neglect.
-
 define <2 x float> @exact_inverse_vec(<2 x float> %x) {
 ; CHECK-LABEL: @exact_inverse_vec(
-; CHECK-NEXT:    [[DIV:%.*]] = fdiv <2 x float> [[X:%.*]], <float 4.000000e+00, float 8.000000e+00>
+; CHECK-NEXT:    [[DIV:%.*]] = fmul <2 x float> [[X:%.*]], <float 2.500000e-01, float 1.250000e-01>
 ; CHECK-NEXT:    ret <2 x float> [[DIV]]
 ;
   %div = fdiv <2 x float> %x, <float 4.0, float 8.0>
@@ -115,6 +113,15 @@ define <2 x float> @not_exact_inverse_vec(<2 x float> %x) {
   ret <2 x float> %div
 }
 
+define <2 x float> @not_exact_inverse_vec_arcp(<2 x float> %x) {
+; CHECK-LABEL: @not_exact_inverse_vec_arcp(
+; CHECK-NEXT:    [[DIV:%.*]] = fmul arcp <2 x float> [[X:%.*]], <float 2.500000e-01, float 0x3FD5555560000000>
+; CHECK-NEXT:    ret <2 x float> [[DIV]]
+;
+  %div = fdiv arcp <2 x float> %x, <float 4.0, float 3.0>
+  ret <2 x float> %div
+}
+
 ; (X / Y) / Z --> X / (Y * Z)
 
 define float @div_with_div_numerator(float %x, float %y, float %z) {
-- 
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