[InstCombine] move/add tests for fmul reassociation; NFC

This transform may be out-of-scope for instcombine, 
but this is only documenting the current behavior.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@326442 91177308-0d34-0410-b5e6-96231b3b80d8

Author: rotateright

test/Transforms/InstCombine/fast-math.ll

@@ -361,18 +361,6 @@ define float @fmul5(float %f1, float %f2) {
   ret float %t3
 }
 
-; (X*Y) * X => (X*X) * Y
-define float @fmul6(float %f1, float %f2) {
-; CHECK-LABEL: @fmul6(
-; CHECK-NEXT:    [[TMP1:%.*]] = fmul fast float [[F1:%.*]], [[F1]]
-; CHECK-NEXT:    [[MUL1:%.*]] = fmul fast float [[TMP1]], [[F2:%.*]]
-; CHECK-NEXT:    ret float [[MUL1]]
-;
-  %mul = fmul float %f1, %f2
-  %mul1 = fmul fast float %mul, %f1
-  ret float %mul1
-}
-
 ; "(X*Y) * X => (X*X) * Y" is disabled if "X*Y" has multiple uses
 define float @fmul7(float %f1, float %f2) {
 ; CHECK-LABEL: @fmul7(

test/Transforms/InstCombine/fmul.ll

@@ -226,3 +226,75 @@ define float @fabs_x_fabs(float %x, float %y) {
   %mul = fmul float %x.fabs, %y.fabs
   ret float %mul
 }
+
+; (X*Y) * X => (X*X) * Y
+
+define float @reassoc_common_operand1(float %x, float %y) {
+; CHECK-LABEL: @reassoc_common_operand1(
+; CHECK-NEXT:    [[TMP1:%.*]] = fmul fast float [[X:%.*]], [[X]]
+; CHECK-NEXT:    [[MUL2:%.*]] = fmul fast float [[TMP1]], [[Y:%.*]]
+; CHECK-NEXT:    ret float [[MUL2]]
+;
+  %mul1 = fmul float %x, %y
+  %mul2 = fmul fast float %mul1, %x
+  ret float %mul2
+}
+
+; (Y*X) * X => (X*X) * Y
+
+define float @reassoc_common_operand2(float %x, float %y) {
+; CHECK-LABEL: @reassoc_common_operand2(
+; CHECK-NEXT:    [[TMP1:%.*]] = fmul fast float [[X:%.*]], [[X]]
+; CHECK-NEXT:    [[MUL2:%.*]] = fmul fast float [[TMP1]], [[Y:%.*]]
+; CHECK-NEXT:    ret float [[MUL2]]
+;
+  %mul1 = fmul float %y, %x
+  %mul2 = fmul fast float %mul1, %x
+  ret float %mul2
+}
+
+; X * (X*Y) => (X*X) * Y
+
+define float @reassoc_common_operand3(float %x1, float %y) {
+; CHECK-LABEL: @reassoc_common_operand3(
+; CHECK-NEXT:    [[X:%.*]] = fdiv float [[X1:%.*]], 3.000000e+00
+; CHECK-NEXT:    [[TMP1:%.*]] = fmul fast float [[X]], [[X]]
+; CHECK-NEXT:    [[MUL2:%.*]] = fmul fast float [[TMP1]], [[Y:%.*]]
+; CHECK-NEXT:    ret float [[MUL2]]
+;
+  %x = fdiv float %x1, 3.0 ; thwart complexity-based canonicalization
+  %mul1 = fmul float %x, %y
+  %mul2 = fmul fast float %x, %mul1
+  ret float %mul2
+}
+
+; X * (Y*X) => (X*X) * Y
+
+define float @reassoc_common_operand4(float %x1, float %y) {
+; CHECK-LABEL: @reassoc_common_operand4(
+; CHECK-NEXT:    [[X:%.*]] = fdiv float [[X1:%.*]], 3.000000e+00
+; CHECK-NEXT:    [[TMP1:%.*]] = fmul fast float [[X]], [[X]]
+; CHECK-NEXT:    [[MUL2:%.*]] = fmul fast float [[TMP1]], [[Y:%.*]]
+; CHECK-NEXT:    ret float [[MUL2]]
+;
+  %x = fdiv float %x1, 3.0 ; thwart complexity-based canonicalization
+  %mul1 = fmul float %y, %x
+  %mul2 = fmul fast float %x, %mul1
+  ret float %mul2
+}
+
+; No change if the first fmul has another use.
+
+define float @reassoc_common_operand_multi_use(float %x, float %y) {
+; CHECK-LABEL: @reassoc_common_operand_multi_use(
+; CHECK-NEXT:    [[MUL1:%.*]] = fmul float [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[MUL2:%.*]] = fmul fast float [[MUL1]], [[X]]
+; CHECK-NEXT:    call void @use_f32(float [[MUL1]])
+; CHECK-NEXT:    ret float [[MUL2]]
+;
+  %mul1 = fmul float %x, %y
+  %mul2 = fmul fast float %mul1, %x
+  call void @use_f32(float %mul1)
+  ret float %mul2
+}
+