[llvm] [SPIRV] Fix compile abort on a switch case value shared with a module constant (PR #223548)

[Diego Novillo via llvm-commits]

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@@ -1118,6 +1118,37 @@ static void insertSpirvDecorations(MachineFunction &MF, SPIRVGlobalRegistry *GR,
     invalidateAndEraseMI(GR, MI);
 }
 
+// Returns the value of the switch case operand defined by Def. For G_CONSTANTs,
+// this is in operand 1. For SPIR-V constants, this is in the literal operands
+// after the type.
+static const ConstantInt *getSwitchCaseValue(const MachineInstr *Def,
+                                             const MachineRegisterInfo &MRI) {
+  if (Def->getOpcode() == TargetOpcode::G_CONSTANT)
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dnovillo wrote:

Done, thanks. I kept the loop over the literal words of a selected `OpConstantI`. I could not find a matcher for that.

https://github.com/llvm/llvm-project/pull/223548