[AArch64] Promote f16 SELECT_CC CC operands when op is legal.

SELECT_CC has the nasty property of having operands with unrelated
types. So if you do something like:

  f32 = select_cc f16, f16, f32, f32, cc

You'd only look for the action for <select_cc, f32>, but never f16.
If the types are all legal, but the op isn't (as for f16 on AArch64,
or for f128 on x86_64/AArch64?), then you get into trouble.
For f128, we have softenSetCCOperands to handle this case.

Similarly, for f16, we can directly promote the CC operands.

llvm-svn: 253344

2 files changed, 34 insertions, 1 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index 14d2f6fb61a..26f03ef765d 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -3887,7 +3887,13 @@ SDValue AArch64TargetLowering::LowerSELECT_CC(ISD::CondCode CC, SDValue LHS,
     }
   }
 
-  // Handle integers first.
+  // Also handle f16, for which we need to do a f32 comparison.
+  if (LHS.getValueType() == MVT::f16) {
+    LHS = DAG.getNode(ISD::FP_EXTEND, dl, MVT::f32, LHS);
+    RHS = DAG.getNode(ISD::FP_EXTEND, dl, MVT::f32, RHS);
+  }
+
+  // Next, handle integers.
   if (LHS.getValueType().isInteger()) {
     assert((LHS.getValueType() == RHS.getValueType()) &&
            (LHS.getValueType() == MVT::i32 || LHS.getValueType() == MVT::i64));
diff --git a/llvm/test/CodeGen/AArch64/f16-instructions.ll b/llvm/test/CodeGen/AArch64/f16-instructions.ll
index 3dd54e64623..ee862850aca 100644
--- a/llvm/test/CodeGen/AArch64/f16-instructions.ll
+++ b/llvm/test/CodeGen/AArch64/f16-instructions.ll
@@ -143,6 +143,33 @@ define half @test_select_cc(half %a, half %b, half %c, half %d) #0 {
   ret half %r
 }
 
+; CHECK-LABEL: test_select_cc_f32_f16:
+; CHECK-DAG:   fcvt s2, h2
+; CHECK-DAG:   fcvt s3, h3
+; CHECK-NEXT:  fcmp s2, s3
+; CHECK-NEXT:  fcsel s0, s0, s1, ne
+; CHECK-NEXT:  ret
+define float @test_select_cc_f32_f16(float %a, float %b, half %c, half %d) #0 {
+  %cc = fcmp une half %c, %d
+  %r = select i1 %cc, float %a, float %b
+  ret float %r
+}
+
+; CHECK-LABEL: test_select_cc_f16_f32:
+; CHECK-DAG:  fcvt s0, h0
+; CHECK-DAG:  fcvt s1, h1
+; CHECK-DAG:  fcmp s2, s3
+; CHECK-DAG:  cset w8, ne
+; CHECK-NEXT: cmp w8, #0
+; CHECK-NEXT: fcsel s0, s0, s1, ne
+; CHECK-NEXT: fcvt h0, s0
+; CHECK-NEXT: ret
+define half @test_select_cc_f16_f32(half %a, half %b, float %c, float %d) #0 {
+  %cc = fcmp une float %c, %d
+  %r = select i1 %cc, half %a, half %b
+  ret half %r
+}
+
 ; CHECK-LABEL: test_fcmp_une:
 ; CHECK-NEXT: fcvt s1, h1
 ; CHECK-NEXT: fcvt s0, h0