[GlobalIsel] [Utility] [NFC] Added isConstantOrConstantSplatVectorFP to handle float constants.

[vg0204]

Needed for #120104

[llvmbot]

@llvm/pr-subscribers-llvm-globalisel

@llvm/pr-subscribers-backend-amdgpu

Author: Vikash Gupta (vg0204)

Changes

Needed for #120104

---

Full diff: https://github.com/llvm/llvm-project/pull/120935.diff

2 Files Affected:

• (modified) llvm/include/llvm/CodeGen/GlobalISel/Utils.h (+7)
• (modified) llvm/lib/CodeGen/GlobalISel/Utils.cpp (+12)

diff --git a/llvm/include/llvm/CodeGen/GlobalISel/Utils.h b/llvm/include/llvm/CodeGen/GlobalISel/Utils.h
index 37653631cc2388..cb5a4c14b364c8 100644
--- a/llvm/include/llvm/CodeGen/GlobalISel/Utils.h
+++ b/llvm/include/llvm/CodeGen/GlobalISel/Utils.h
@@ -522,6 +522,13 @@ std::optional<APInt>
 isConstantOrConstantSplatVector(MachineInstr &MI,
                                 const MachineRegisterInfo &MRI);
 
+/// Determines if \p MI defines a float constant integer or a splat vector of
+/// float constant integers.
+/// \returns the float constant or std::nullopt.
+std::optional<APFloat>
+isConstantOrConstantSplatVectorFP(MachineInstr &MI,
+                                  const MachineRegisterInfo &MRI);
+
 /// Attempt to match a unary predicate against a scalar/splat constant or every
 /// element of a constant G_BUILD_VECTOR. If \p ConstVal is null, the source
 /// value was undef.
diff --git a/llvm/lib/CodeGen/GlobalISel/Utils.cpp b/llvm/lib/CodeGen/GlobalISel/Utils.cpp
index 8c1e41ea106eca..79382933a1f42d 100644
--- a/llvm/lib/CodeGen/GlobalISel/Utils.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/Utils.cpp
@@ -1517,6 +1517,18 @@ llvm::isConstantOrConstantSplatVector(MachineInstr &MI,
   return APInt(ScalarSize, *MaybeCst, true);
 }
 
+std::optional<APFloat>
+llvm::isConstantOrConstantSplatVectorFP(MachineInstr &MI,
+                                        const MachineRegisterInfo &MRI) {
+  Register Def = MI.getOperand(0).getReg();
+  if (auto FpConst = getFConstantVRegValWithLookThrough(Def, MRI))
+    return FpConst->Value;
+  auto MaybeCstFP = getFConstantSplat(Def, MRI, /*allowUndef=*/false);
+  if (!MaybeCstFP)
+    return std::nullopt;
+  return MaybeCstFP->Value;
+}
+
 bool llvm::isNullOrNullSplat(const MachineInstr &MI,
                              const MachineRegisterInfo &MRI, bool AllowUndefs) {
   switch (MI.getOpcode()) {

[arsenm]

I thought we had switched the integer versions over to using ConstantInt* to avoid temporary copies of APInt, but I see the integer version above isn't doing that. We can change the pair as a set later

[arsenm]

Unit test wouldn't hurt

[vg0204]

Unit test wouldn't hurt

Can you once review @arsenm!