[InstCombine] add test to show fmul transform creates extra fdiv; NFC

Also, move fmul reassociation tests to the same file as other fmul transforms.

llvm-svn: 327342

2 files changed, 107 insertions, 88 deletions

diff --git a/llvm/test/Transforms/InstCombine/fast-math.ll b/llvm/test/Transforms/InstCombine/fast-math.ll
index 6c251c355cf..96d70dbdfc4 100644
--- a/llvm/test/Transforms/InstCombine/fast-math.ll
+++ b/llvm/test/Transforms/InstCombine/fast-math.ll
@@ -273,94 +273,6 @@ define float @fmul_distribute4(float %f1) {
   ret float %t3
 }
 
-; C1/X * C2 => (C1*C2) / X
-define float @fmul2(float %f1) {
-; CHECK-LABEL: @fmul2(
-; CHECK-NEXT:    [[TMP1:%.*]] = fdiv fast float 1.200000e+07, [[F1:%.*]]
-; CHECK-NEXT:    ret float [[TMP1]]
-;
-  %t1 = fdiv float 2.0e+3, %f1
-  %t3 = fmul fast float %t1, 6.0e+3
-  ret float %t3
-}
-
-; X/C1 * C2 => X * (C2/C1) is disabled if X/C1 has multiple uses
-@fmul2_external = external global float
-define float @fmul2_disable(float %f1) {
-; CHECK-LABEL: @fmul2_disable(
-; CHECK-NEXT:    [[DIV:%.*]] = fdiv fast float 1.000000e+00, [[F1:%.*]]
-; CHECK-NEXT:    store float [[DIV]], float* @fmul2_external, align 4
-; CHECK-NEXT:    [[MUL:%.*]] = fmul fast float [[DIV]], 2.000000e+00
-; CHECK-NEXT:    ret float [[MUL]]
-;
-  %div = fdiv fast float 1.000000e+00, %f1
-  store float %div, float* @fmul2_external
-  %mul = fmul fast float %div, 2.000000e+00
-  ret float %mul
-}
-
-; X/C1 * C2 => X * (C2/C1) (if C2/C1 is normal Fp)
-define float @fmul3(float %f1, float %f2) {
-; CHECK-LABEL: @fmul3(
-; CHECK-NEXT:    [[TMP1:%.*]] = fmul fast float [[F1:%.*]], 3.000000e+00
-; CHECK-NEXT:    ret float [[TMP1]]
-;
-  %t1 = fdiv float %f1, 2.0e+3
-  %t3 = fmul fast float %t1, 6.0e+3
-  ret float %t3
-}
-
-define <4 x float> @fmul3_vec(<4 x float> %f1, <4 x float> %f2) {
-; CHECK-LABEL: @fmul3_vec(
-; CHECK-NEXT:    [[TMP1:%.*]] = fmul fast <4 x float> [[F1:%.*]], <float 3.000000e+00, float 2.000000e+00, float 1.000000e+00, float 1.000000e+00>
-; CHECK-NEXT:    ret <4 x float> [[TMP1]]
-;
-  %t1 = fdiv <4 x float> %f1, <float 2.0e+3, float 3.0e+3, float 2.0e+3, float 1.0e+3>
-  %t3 = fmul fast <4 x float> %t1, <float 6.0e+3, float 6.0e+3, float 2.0e+3, float 1.0e+3>
-  ret <4 x float> %t3
-}
-
-; Make sure fmul with constant expression doesn't assert.
-define <4 x float> @fmul3_vec_constexpr(<4 x float> %f1, <4 x float> %f2) {
-; CHECK-LABEL: @fmul3_vec_constexpr(
-; CHECK-NEXT:    [[TMP1:%.*]] = fmul fast <4 x float> [[F1:%.*]], <float 3.000000e+00, float 2.000000e+00, float 1.000000e+00, float 1.000000e+00>
-; CHECK-NEXT:    ret <4 x float> [[TMP1]]
-;
-  %constExprMul = bitcast i128 trunc (i160 bitcast (<5 x float> <float 6.0e+3, float 6.0e+3, float 2.0e+3, float 1.0e+3, float undef> to i160) to i128) to <4 x float>
-  %t1 = fdiv <4 x float> %f1, <float 2.0e+3, float 3.0e+3, float 2.0e+3, float 1.0e+3>
-  %t3 = fmul fast <4 x float> %t1, %constExprMul
-  ret <4 x float> %t3
-}
-
-; Rule "X/C1 * C2 => X * (C2/C1) is not applicable if C2/C1 is either a special
-; value of a denormal. The 0x3810000000000000 here take value FLT_MIN
-;
-define float @fmul4(float %f1, float %f2) {
-; CHECK-LABEL: @fmul4(
-; CHECK-NEXT:    [[T1:%.*]] = fdiv float [[F1:%.*]], 2.000000e+03
-; CHECK-NEXT:    [[T3:%.*]] = fmul fast float [[T1]], 0x3810000000000000
-; CHECK-NEXT:    ret float [[T3]]
-;
-  %t1 = fdiv float %f1, 2.0e+3
-  %t3 = fmul fast float %t1, 0x3810000000000000
-  ret float %t3
-}
-
-; 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
-; CHECK-NEXT:    ret float [[TMP1]]
-;
-  %t1 = fdiv float %f1, 3.0e+0
-  %t3 = fmul fast float %t1, 0x3810000000000000
-  ret float %t3
-}
-
 ; "(X*Y) * X => (X*X) * Y" is disabled if "X*Y" has multiple uses
 define float @fmul7(float %f1, float %f2) {
 ; CHECK-LABEL: @fmul7(
diff --git a/llvm/test/Transforms/InstCombine/fmul.ll b/llvm/test/Transforms/InstCombine/fmul.ll
index 3637f6c2b59..0cfcb336c73 100644
--- a/llvm/test/Transforms/InstCombine/fmul.ll
+++ b/llvm/test/Transforms/InstCombine/fmul.ll
@@ -332,3 +332,110 @@ define float @log2half_commute(float %x1, float %y) {
   ret float %mul
 }
 
+; C1/X * C2 => (C1*C2) / X
+
+define float @fdiv_constant_numerator_fmul(float %x) {
+; CHECK-LABEL: @fdiv_constant_numerator_fmul(
+; CHECK-NEXT:    [[TMP1:%.*]] = fdiv fast float 1.200000e+07, [[X:%.*]]
+; CHECK-NEXT:    ret float [[TMP1]]
+;
+  %t1 = fdiv float 2.0e+3, %x
+  %t3 = fmul fast float %t1, 6.0e+3
+  ret float %t3
+}
+
+; C1/X * C2 => (C1*C2) / X is disabled if C1/X has multiple uses
+
+@fmul2_external = external global float
+
+define float @fdiv_constant_numerator_fmul_extra_use(float %x) {
+; CHECK-LABEL: @fdiv_constant_numerator_fmul_extra_use(
+; CHECK-NEXT:    [[DIV:%.*]] = fdiv fast float 1.000000e+00, [[X:%.*]]
+; CHECK-NEXT:    store float [[DIV]], float* @fmul2_external, align 4
+; CHECK-NEXT:    [[MUL:%.*]] = fmul fast float [[DIV]], 2.000000e+00
+; CHECK-NEXT:    ret float [[MUL]]
+;
+  %div = fdiv fast float 1.0, %x
+  store float %div, float* @fmul2_external
+  %mul = fmul fast float %div, 2.0
+  ret float %mul
+}
+
+; X/C1 * C2 => X * (C2/C1) (if C2/C1 is normal FP)
+
+define float @fdiv_constant_denominator_fmul(float %x) {
+; CHECK-LABEL: @fdiv_constant_denominator_fmul(
+; CHECK-NEXT:    [[TMP1:%.*]] = fmul fast float [[X:%.*]], 3.000000e+00
+; CHECK-NEXT:    ret float [[TMP1]]
+;
+  %t1 = fdiv float %x, 2.0e+3
+  %t3 = fmul fast float %t1, 6.0e+3
+  ret float %t3
+}
+
+define <4 x float> @fdiv_constant_denominator_fmul_vec(<4 x float> %x) {
+; CHECK-LABEL: @fdiv_constant_denominator_fmul_vec(
+; CHECK-NEXT:    [[TMP1:%.*]] = fmul fast <4 x float> [[X:%.*]], <float 3.000000e+00, float 2.000000e+00, float 1.000000e+00, float 1.000000e+00>
+; CHECK-NEXT:    ret <4 x float> [[TMP1]]
+;
+  %t1 = fdiv <4 x float> %x, <float 2.0e+3, float 3.0e+3, float 2.0e+3, float 1.0e+3>
+  %t3 = fmul fast <4 x float> %t1, <float 6.0e+3, float 6.0e+3, float 2.0e+3, float 1.0e+3>
+  ret <4 x float> %t3
+}
+
+; Make sure fmul with constant expression doesn't assert.
+
+define <4 x float> @fdiv_constant_denominator_fmul_vec_constexpr(<4 x float> %x) {
+; CHECK-LABEL: @fdiv_constant_denominator_fmul_vec_constexpr(
+; CHECK-NEXT:    [[TMP1:%.*]] = fmul fast <4 x float> [[X:%.*]], <float 3.000000e+00, float 2.000000e+00, float 1.000000e+00, float 1.000000e+00>
+; CHECK-NEXT:    ret <4 x float> [[TMP1]]
+;
+  %constExprMul = bitcast i128 trunc (i160 bitcast (<5 x float> <float 6.0e+3, float 6.0e+3, float 2.0e+3, float 1.0e+3, float undef> to i160) to i128) to <4 x float>
+  %t1 = fdiv <4 x float> %x, <float 2.0e+3, float 3.0e+3, float 2.0e+3, float 1.0e+3>
+  %t3 = fmul fast <4 x float> %t1, %constExprMul
+  ret <4 x float> %t3
+}
+
+; Rule "X/C1 * C2 => X * (C2/C1) is not applicable if C2/C1 is abnormal
+; 0x3810000000000000 == FLT_MIN
+
+define float @fdiv_constant_denominator_fmul_denorm(float %x) {
+; CHECK-LABEL: @fdiv_constant_denominator_fmul_denorm(
+; CHECK-NEXT:    [[T1:%.*]] = fdiv float [[X:%.*]], 2.000000e+03
+; CHECK-NEXT:    [[T3:%.*]] = fmul fast float [[T1]], 0x3810000000000000
+; CHECK-NEXT:    ret float [[T3]]
+;
+  %t1 = fdiv float %x, 2.0e+3
+  %t3 = fmul fast float %t1, 0x3810000000000000
+  ret float %t3
+}
+
+; X / C1 * C2 => X / (C2/C1) if C1/C2 is abnormal, but 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 @fdiv_constant_denominator_fmul_denorm_try_harder(float %x) {
+; CHECK-LABEL: @fdiv_constant_denominator_fmul_denorm_try_harder(
+; CHECK-NEXT:    [[TMP1:%.*]] = fdiv fast float [[X:%.*]], 0x47E8000000000000
+; CHECK-NEXT:    ret float [[TMP1]]
+;
+  %t1 = fdiv float %x, 3.0
+  %t3 = fmul fast float %t1, 0x3810000000000000
+  ret float %t3
+}
+
+; FIXME: We have 2 divisions instead of the 1 we started with.
+
+define float @fdiv_constant_denominator_fmul_denorm_try_harder_extra_use(float %x) {
+; CHECK-LABEL: @fdiv_constant_denominator_fmul_denorm_try_harder_extra_use(
+; CHECK-NEXT:    [[T1:%.*]] = fdiv float [[X:%.*]], 3.000000e+00
+; CHECK-NEXT:    [[TMP1:%.*]] = fdiv fast float [[X]], 0x47E8000000000000
+; CHECK-NEXT:    [[R:%.*]] = fadd float [[T1]], [[TMP1]]
+; CHECK-NEXT:    ret float [[R]]
+;
+  %t1 = fdiv float %x, 3.0e+0
+  %t3 = fmul fast float %t1, 0x3810000000000000
+  %r = fadd float %t1, %t3
+  ret float %r
+}
+