Imported Upstream version 5.18.0.179

Former-commit-id: 67aa10e65b237e1c4537630979ee99ebe1374215

external/llvm/test/Transforms/InstCombine/fsub.ll

@@ -0,0 +1,67 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+; PR4374
+define float @test1(float %a, float %b) nounwind {
+  %t1 = fsub float %a, %b
+  %t2 = fsub float -0.000000e+00, %t1
+
+; CHECK:       %t1 = fsub float %a, %b
+; CHECK-NEXT:  %t2 = fsub float -0.000000e+00, %t1
+
+  ret float %t2
+}
+
+; <rdar://problem/7530098>
+define double @test2(double %x, double %y) nounwind {
+  %t1 = fadd double %x, %y
+  %t2 = fsub double %x, %t1
+
+; CHECK:      %t1 = fadd double %x, %y
+; CHECK-NEXT: %t2 = fsub double %x, %t1
+
+  ret double %t2
+}
+
+; CHECK-LABEL: @fsub_undef(
+; CHECK: %sub = fsub float %val, undef
+define float @fsub_undef(float %val) {
+bb:
+  %sub = fsub float %val, undef
+  ret float %sub
+}
+
+; XXX - Why doesn't this fold to undef?
+; CHECK-LABEL: @fsub_fast_undef(
+; CHCK: %sub = fsub fast float %val, undef
+define float @fsub_fast_undef(float %val) {
+bb:
+  %sub = fsub fast float %val, undef
+  ret float %sub
+}
+
+; CHECK-LABEL: @fneg_undef(
+; CHECK: ret float fsub (float -0.000000e+00, float undef)
+define float @fneg_undef(float %val) {
+bb:
+  %sub = fsub float -0.0, undef
+  ret float %sub
+}
+
+; CHECK-LABEL: @fneg_fast_undef(
+; CHECK: ret float fsub (float -0.000000e+00, float undef)
+define float @fneg_fast_undef(float %val) {
+bb:
+  %sub = fsub fast float -0.0, undef
+  ret float %sub
+}
+
+; This folds to a constant expression, which produced 0 instructions
+; contrary to the expected one for negation.
+; CHECK-LABEL: @inconsistent_numbers_fsub_undef(
+; CHECK: ret float fsub (float -0.000000e+00, float undef)
+define float @inconsistent_numbers_fsub_undef(float %val) {
+bb:
+  %sub0 = fsub fast float %val, undef
+  %sub1 = fsub fast float %sub0, %val
+  ret float %sub1
+}