[InstCombine] add test for loop-invariant fdiv; NFC

Adding baseline test based on D87479, so we know
current state and limitations of a potential fix.

llvm/test/Transforms/InstCombine/fmul.ll

@@ -1051,6 +1051,42 @@ define float @fmul_fdiv_factor_extra_use(float %x, float %y) {
   ret float %mul
 }
 
+define void @fmul_loop_invariant_fdiv(float* %a, float %x) {
+; CHECK-LABEL: @fmul_loop_invariant_fdiv(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
+; CHECK:       for.cond.cleanup:
+; CHECK-NEXT:    ret void
+; CHECK:       for.body:
+; CHECK-NEXT:    [[I_08:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[INC:%.*]], [[FOR_BODY]] ]
+; CHECK-NEXT:    [[IDXPROM:%.*]] = zext i32 [[I_08]] to i64
+; CHECK-NEXT:    [[ARRAYIDX:%.*]] = getelementptr inbounds float, ptr [[A:%.*]], i64 [[IDXPROM]]
+; CHECK-NEXT:    [[F:%.*]] = load float, ptr [[ARRAYIDX]], align 4
+; CHECK-NEXT:    [[M:%.*]] = fdiv fast float [[F]], [[X:%.*]]
+; CHECK-NEXT:    store float [[M]], ptr [[ARRAYIDX]], align 4
+; CHECK-NEXT:    [[INC]] = add nuw nsw i32 [[I_08]], 1
+; CHECK-NEXT:    [[CMP_NOT:%.*]] = icmp eq i32 [[INC]], 1024
+; CHECK-NEXT:    br i1 [[CMP_NOT]], label [[FOR_COND_CLEANUP:%.*]], label [[FOR_BODY]]
+;
+entry:
+  %d = fdiv fast float 1.0, %x
+  br label %for.body
+
+for.cond.cleanup:
+  ret void
+
+for.body:
+  %i.08 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  %idxprom = zext i32 %i.08 to i64
+  %arrayidx = getelementptr inbounds float, float* %a, i64 %idxprom
+  %f = load float, float* %arrayidx, align 4
+  %m = fmul fast float %f, %d
+  store float %m, float* %arrayidx, align 4
+  %inc = add nuw nsw i32 %i.08, 1
+  %cmp.not = icmp eq i32 %inc, 1024
+  br i1 %cmp.not, label %for.cond.cleanup, label %for.body
+}
+
 ; Avoid infinite looping by moving negation out of a constant expression.
 
 @g = external global {[2 x ptr]}, align 1
@@ -1069,8 +1105,8 @@ define double @fmul_negated_constant_expression(double %x) {
 define float @negate_if_true(float %x, i1 %cond) {
 ; CHECK-LABEL: @negate_if_true(
 ; CHECK-NEXT:    [[TMP1:%.*]] = fneg float [[X:%.*]]
-; CHECK-NEXT:    [[TMP2:%.*]] = select i1 [[COND:%.*]], float [[TMP1]], float [[X]]
-; CHECK-NEXT:    ret float [[TMP2]]
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[COND:%.*]], float [[TMP1]], float [[X]]
+; CHECK-NEXT:    ret float [[R]]
 ;
   %sel = select i1 %cond, float -1.0, float 1.0
   %r = fmul float %sel, %x
@@ -1080,8 +1116,8 @@ define float @negate_if_true(float %x, i1 %cond) {
 define float @negate_if_false(float %x, i1 %cond) {
 ; CHECK-LABEL: @negate_if_false(
 ; CHECK-NEXT:    [[TMP1:%.*]] = fneg arcp float [[X:%.*]]
-; CHECK-NEXT:    [[TMP2:%.*]] = select arcp i1 [[COND:%.*]], float [[X]], float [[TMP1]]
-; CHECK-NEXT:    ret float [[TMP2]]
+; CHECK-NEXT:    [[R:%.*]] = select arcp i1 [[COND:%.*]], float [[X]], float [[TMP1]]
+; CHECK-NEXT:    ret float [[R]]
 ;
   %sel = select i1 %cond, float 1.0, float -1.0
   %r = fmul arcp float %sel, %x
@@ -1092,8 +1128,8 @@ define <2 x double> @negate_if_true_commute(<2 x double> %px, i1 %cond) {
 ; CHECK-LABEL: @negate_if_true_commute(
 ; CHECK-NEXT:    [[X:%.*]] = fdiv <2 x double> <double 4.200000e+01, double 4.200000e+01>, [[PX:%.*]]
 ; CHECK-NEXT:    [[TMP1:%.*]] = fneg ninf <2 x double> [[X]]
-; CHECK-NEXT:    [[TMP2:%.*]] = select ninf i1 [[COND:%.*]], <2 x double> [[TMP1]], <2 x double> [[X]]
-; CHECK-NEXT:    ret <2 x double> [[TMP2]]
+; CHECK-NEXT:    [[R:%.*]] = select ninf i1 [[COND:%.*]], <2 x double> [[TMP1]], <2 x double> [[X]]
+; CHECK-NEXT:    ret <2 x double> [[R]]
 ;
   %x = fdiv <2 x double> <double 42.0, double 42.0>, %px  ; thwart complexity-based canonicalization
   %sel = select i1 %cond, <2 x double> <double -1.0, double -1.0>, <2 x double> <double 1.0, double 1.0>
@@ -1105,8 +1141,8 @@ define <2 x double> @negate_if_false_commute(<2 x double> %px, <2 x i1> %cond) {
 ; CHECK-LABEL: @negate_if_false_commute(
 ; CHECK-NEXT:    [[X:%.*]] = fdiv <2 x double> <double 4.200000e+01, double 5.100000e+00>, [[PX:%.*]]
 ; CHECK-NEXT:    [[TMP1:%.*]] = fneg <2 x double> [[X]]
-; CHECK-NEXT:    [[TMP2:%.*]] = select <2 x i1> [[COND:%.*]], <2 x double> [[X]], <2 x double> [[TMP1]]
-; CHECK-NEXT:    ret <2 x double> [[TMP2]]
+; CHECK-NEXT:    [[R:%.*]] = select <2 x i1> [[COND:%.*]], <2 x double> [[X]], <2 x double> [[TMP1]]
+; CHECK-NEXT:    ret <2 x double> [[R]]
 ;
   %x = fdiv <2 x double> <double 42.0, double 5.1>, %px  ; thwart complexity-based canonicalization
   %sel = select <2 x i1> %cond, <2 x double> <double 1.0, double 1.0>, <2 x double> <double -1.0, double -1.0>
@@ -1203,8 +1239,8 @@ define <vscale x 2 x float> @mul_scalable_splat_zero(<vscale x 2 x float> %z) {
 
 define half @mul_zero_nnan(half %x) {
 ; CHECK-LABEL: @mul_zero_nnan(
-; CHECK-NEXT:    [[TMP1:%.*]] = call nnan half @llvm.copysign.f16(half 0xH0000, half [[X:%.*]])
-; CHECK-NEXT:    ret half [[TMP1]]
+; CHECK-NEXT:    [[R:%.*]] = call nnan half @llvm.copysign.f16(half 0xH0000, half [[X:%.*]])
+; CHECK-NEXT:    ret half [[R]]
 ;
   %r = fmul nnan half %x, 0.0
   ret half %r
@@ -1214,8 +1250,8 @@ define half @mul_zero_nnan(half %x) {
 
 define <2 x float> @mul_zero_nnan_vec_poison(<2 x float> %x) {
 ; CHECK-LABEL: @mul_zero_nnan_vec_poison(
-; CHECK-NEXT:    [[TMP1:%.*]] = call nnan <2 x float> @llvm.copysign.v2f32(<2 x float> <float 0.000000e+00, float poison>, <2 x float> [[X:%.*]])
-; CHECK-NEXT:    ret <2 x float> [[TMP1]]
+; CHECK-NEXT:    [[R:%.*]] = call nnan <2 x float> @llvm.copysign.v2f32(<2 x float> <float 0.000000e+00, float poison>, <2 x float> [[X:%.*]])
+; CHECK-NEXT:    ret <2 x float> [[R]]
 ;
   %r = fmul nnan <2 x float> %x, <float 0.0, float poison>
   ret <2 x float> %r