[AArch64][GlobalISel] Widen scalar int->fp conversions.

It's incorrect to ignore the higher bits of the integer source.
Teach the legalizer how to widen it.

llvm-svn: 292563

2 files changed, 29 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index 5f23d253f56..f77d807a69d 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -273,6 +273,28 @@ LegalizerHelper::widenScalar(MachineInstr &MI, unsigned TypeIdx, LLT WideTy) {
     MI.eraseFromParent();
     return Legalized;
   }
+  case TargetOpcode::G_SITOFP:
+  case TargetOpcode::G_UITOFP: {
+    if (TypeIdx != 1)
+      return UnableToLegalize;
+
+    unsigned Src = MI.getOperand(1).getReg();
+    unsigned SrcExt = MRI.createGenericVirtualRegister(WideTy);
+
+    if (MI.getOpcode() == TargetOpcode::G_SITOFP) {
+      MIRBuilder.buildSExt(SrcExt, Src);
+    } else {
+      assert(MI.getOpcode() == TargetOpcode::G_UITOFP && "Unexpected conv op");
+      MIRBuilder.buildZExt(SrcExt, Src);
+    }
+
+    MIRBuilder.buildInstr(MI.getOpcode())
+        .addDef(MI.getOperand(0).getReg())
+        .addUse(SrcExt);
+
+    MI.eraseFromParent();
+    return Legalized;
+  }
   case TargetOpcode::G_LOAD: {
     assert(alignTo(MRI.getType(MI.getOperand(0).getReg()).getSizeInBits(), 8) ==
                WideTy.getSizeInBits() &&
diff --git a/llvm/lib/Target/AArch64/AArch64LegalizerInfo.cpp b/llvm/lib/Target/AArch64/AArch64LegalizerInfo.cpp
index 48838f28b4b..dad390b752c 100644
--- a/llvm/lib/Target/AArch64/AArch64LegalizerInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64LegalizerInfo.cpp
@@ -141,12 +141,18 @@ AArch64LegalizerInfo::AArch64LegalizerInfo() {
     setAction({G_TRUNC, 1, Ty}, Legal);
 
   // Conversions
-  for (auto Ty : { s1, s8, s16, s32, s64 }) {
+  for (auto Ty : { s32, s64 }) {
     setAction({G_FPTOSI, 0, Ty}, Legal);
     setAction({G_FPTOUI, 0, Ty}, Legal);
     setAction({G_SITOFP, 1, Ty}, Legal);
     setAction({G_UITOFP, 1, Ty}, Legal);
   }
+  for (auto Ty : { s1, s8, s16 }) {
+    setAction({G_FPTOSI, 0, Ty}, Legal);
+    setAction({G_FPTOUI, 0, Ty}, Legal);
+    setAction({G_SITOFP, 1, Ty}, WidenScalar);
+    setAction({G_UITOFP, 1, Ty}, WidenScalar);
+  }
 
   for (auto Ty : { s32, s64 }) {
     setAction({G_FPTOSI, 1, Ty}, Legal);