[DAGCombiner] loosen constraints for fsub+fadd fold

isNegatibleForFree() should not matter here (as the test diffs show)
because it's always a win to replace an fsub+fadd with fneg. The
problem in D50195 persists because either (1) we are doing these
folds in the wrong order or (2) we're missing another fold for fadd.

llvm-svn: 339299

1 files changed, 44 insertions, 24 deletions

diff --git a/llvm/test/CodeGen/X86/fp-fold.ll b/llvm/test/CodeGen/X86/fp-fold.ll
index 917b5d368dd..1102b755130 100644
--- a/llvm/test/CodeGen/X86/fp-fold.ll
+++ b/llvm/test/CodeGen/X86/fp-fold.ll
@@ -113,12 +113,17 @@ define float @fsub_neg_y(float %x, float %y) {
 ; Y - (X + Y) --> -X
 
 define float @fsub_fadd_common_op_fneg(float %x, float %y) {
-; ANY-LABEL: fsub_fadd_common_op_fneg:
-; ANY:       # %bb.0:
-; ANY-NEXT:    addss %xmm1, %xmm0
-; ANY-NEXT:    subss %xmm0, %xmm1
-; ANY-NEXT:    movaps %xmm1, %xmm0
-; ANY-NEXT:    retq
+; STRICT-LABEL: fsub_fadd_common_op_fneg:
+; STRICT:       # %bb.0:
+; STRICT-NEXT:    addss %xmm1, %xmm0
+; STRICT-NEXT:    subss %xmm0, %xmm1
+; STRICT-NEXT:    movaps %xmm1, %xmm0
+; STRICT-NEXT:    retq
+;
+; UNSAFE-LABEL: fsub_fadd_common_op_fneg:
+; UNSAFE:       # %bb.0:
+; UNSAFE-NEXT:    xorps {{.*}}(%rip), %xmm0
+; UNSAFE-NEXT:    retq
   %a = fadd float %x, %y
   %r = fsub reassoc nsz float %y, %a
   ret float %r
@@ -127,12 +132,17 @@ define float @fsub_fadd_common_op_fneg(float %x, float %y) {
 ; Y - (X + Y) --> -X
 
 define <4 x float> @fsub_fadd_common_op_fneg_vec(<4 x float> %x, <4 x float> %y) {
-; ANY-LABEL: fsub_fadd_common_op_fneg_vec:
-; ANY:       # %bb.0:
-; ANY-NEXT:    addps %xmm1, %xmm0
-; ANY-NEXT:    subps %xmm0, %xmm1
-; ANY-NEXT:    movaps %xmm1, %xmm0
-; ANY-NEXT:    retq
+; STRICT-LABEL: fsub_fadd_common_op_fneg_vec:
+; STRICT:       # %bb.0:
+; STRICT-NEXT:    addps %xmm1, %xmm0
+; STRICT-NEXT:    subps %xmm0, %xmm1
+; STRICT-NEXT:    movaps %xmm1, %xmm0
+; STRICT-NEXT:    retq
+;
+; UNSAFE-LABEL: fsub_fadd_common_op_fneg_vec:
+; UNSAFE:       # %bb.0:
+; UNSAFE-NEXT:    xorps {{.*}}(%rip), %xmm0
+; UNSAFE-NEXT:    retq
   %a = fadd <4 x float> %x, %y
   %r = fsub nsz reassoc <4 x float> %y, %a
   ret <4 x float> %r
@@ -142,12 +152,17 @@ define <4 x float> @fsub_fadd_common_op_fneg_vec(<4 x float> %x, <4 x float> %y)
 ; Commute operands of the 'add'.
 
 define float @fsub_fadd_common_op_fneg_commute(float %x, float %y) {
-; ANY-LABEL: fsub_fadd_common_op_fneg_commute:
-; ANY:       # %bb.0:
-; ANY-NEXT:    addss %xmm1, %xmm0
-; ANY-NEXT:    subss %xmm0, %xmm1
-; ANY-NEXT:    movaps %xmm1, %xmm0
-; ANY-NEXT:    retq
+; STRICT-LABEL: fsub_fadd_common_op_fneg_commute:
+; STRICT:       # %bb.0:
+; STRICT-NEXT:    addss %xmm1, %xmm0
+; STRICT-NEXT:    subss %xmm0, %xmm1
+; STRICT-NEXT:    movaps %xmm1, %xmm0
+; STRICT-NEXT:    retq
+;
+; UNSAFE-LABEL: fsub_fadd_common_op_fneg_commute:
+; UNSAFE:       # %bb.0:
+; UNSAFE-NEXT:    xorps {{.*}}(%rip), %xmm0
+; UNSAFE-NEXT:    retq
   %a = fadd float %y, %x
   %r = fsub reassoc nsz float %y, %a
   ret float %r
@@ -156,12 +171,17 @@ define float @fsub_fadd_common_op_fneg_commute(float %x, float %y) {
 ; Y - (Y + X) --> -X
 
 define <4 x float> @fsub_fadd_common_op_fneg_commute_vec(<4 x float> %x, <4 x float> %y) {
-; ANY-LABEL: fsub_fadd_common_op_fneg_commute_vec:
-; ANY:       # %bb.0:
-; ANY-NEXT:    addps %xmm1, %xmm0
-; ANY-NEXT:    subps %xmm0, %xmm1
-; ANY-NEXT:    movaps %xmm1, %xmm0
-; ANY-NEXT:    retq
+; STRICT-LABEL: fsub_fadd_common_op_fneg_commute_vec:
+; STRICT:       # %bb.0:
+; STRICT-NEXT:    addps %xmm1, %xmm0
+; STRICT-NEXT:    subps %xmm0, %xmm1
+; STRICT-NEXT:    movaps %xmm1, %xmm0
+; STRICT-NEXT:    retq
+;
+; UNSAFE-LABEL: fsub_fadd_common_op_fneg_commute_vec:
+; UNSAFE:       # %bb.0:
+; UNSAFE-NEXT:    xorps {{.*}}(%rip), %xmm0
+; UNSAFE-NEXT:    retq
   %a = fadd <4 x float> %y, %x
   %r = fsub reassoc nsz <4 x float> %y, %a
   ret <4 x float> %r