[llvm][MIRVRegNamerUtils] Adding hashing on CImm / FPImm MachineOpera…

…nds.

This patch makes it so that cases where multiple instructions that
differ only in their ConstantInt or ConstantFP MachineOperand values no
longer collide. For instance:

%0:_(s1) = G_CONSTANT i1 true
%1:_(s1) = G_CONSTANT i1 false
%2:_(s32) = G_FCONSTANT float 1.0
%3:_(s32) = G_FCONSTANT float 0.0

Prior to this patch the first two instructions would collide together.
Also, the last two G_FCONSTANT instructions would also collide. Now they
will no longer collide.

Differential Revision: https://reviews.llvm.org/D71558

llvm/lib/CodeGen/MIRVRegNamerUtils.cpp

@@ -53,6 +53,13 @@ std::string VRegRenamer::getInstructionOpcodeHash(MachineInstr &MI) {
   // Gets a hashable artifact from a given MachineOperand (ie an unsigned).
   auto GetHashableMO = [this](const MachineOperand &MO) -> unsigned {
     switch (MO.getType()) {
+    case MachineOperand::MO_CImmediate:
+      return hash_combine(MO.getType(), MO.getTargetFlags(),
+                          MO.getCImm()->getZExtValue());
+    case MachineOperand::MO_FPImmediate:
+      return hash_combine(
+          MO.getType(), MO.getTargetFlags(),
+          MO.getFPImm()->getValueAPF().bitcastToAPInt().getZExtValue());
     case MachineOperand::MO_Immediate:
       return MO.getImm();
     case MachineOperand::MO_TargetIndex:
@@ -70,8 +77,6 @@ std::string VRegRenamer::getInstructionOpcodeHash(MachineInstr &MI) {
 
     // TODO: Handle the following Immediate/Index/ID/Predicate cases. They can
     // be hashed on in a stable manner.
-    case MachineOperand::MO_CImmediate:
-    case MachineOperand::MO_FPImmediate:
     case MachineOperand::MO_FrameIndex:
     case MachineOperand::MO_ConstantPoolIndex:
     case MachineOperand::MO_JumpTableIndex:

llvm/test/CodeGen/MIR/Generic/CFPImmMIRCanonHash.mir

@@ -0,0 +1,14 @@
+# RUN: llc -run-pass mir-canonicalizer -o - %s | FileCheck %s
+---
+name: cimm_fpimm_hash_test
+body: |
+  bb.0:
+    ; CHECK: _1:_(s1) = G_CONSTANT i1 true
+    ; CHECK: _1:_(s1) = G_CONSTANT i1 false
+    ; CHECK: _1:_(s32) = G_FCONSTANT float
+    ; CHECK: _1:_(s32) = G_FCONSTANT float
+    %0:_(s1) = G_CONSTANT i1 true
+    %1:_(s1) = G_CONSTANT i1 false
+    %2:_(s32) = G_FCONSTANT float 1.0
+    %3:_(s32) = G_FCONSTANT float 0.0
+...