[PATCH] D128876: [RISCV] Fix wrong register rename for store value during make-compressible optimization

[Kito Cheng via Phabricator via llvm-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG5c45ae4108d3: [RISCV] Fix wrong register rename for store value during make-compressible… (authored by kito-cheng).

Changed prior to commit:
  https://reviews.llvm.org/D128876?vs=442430&id=443187#toc

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D128876/new/

https://reviews.llvm.org/D128876

Files:
  llvm/lib/Target/RISCV/RISCVMakeCompressible.cpp
  llvm/test/CodeGen/RISCV/make-compressible-for-store-address.mir


Index: llvm/test/CodeGen/RISCV/make-compressible-for-store-address.mir
===================================================================
--- llvm/test/CodeGen/RISCV/make-compressible-for-store-address.mir
+++ llvm/test/CodeGen/RISCV/make-compressible-for-store-address.mir
@@ -33,7 +33,7 @@
     ; CHECK-NEXT: renamable $x11 = ADDI $x0, 1
     ; CHECK-NEXT: $x12 = ADDI $x10, 768
     ; CHECK-NEXT: SD killed renamable $x11, $x12, 32 :: (store (s64) into %ir.1)
-    ; CHECK-NEXT: SD $x12, $x12, 40 :: (store (s64) into %ir.2)
+    ; CHECK-NEXT: SD renamable $x10, $x12, 40 :: (store (s64) into %ir.2)
     ; CHECK-NEXT: renamable $x11 = ADDI $x0, 2
     ; CHECK-NEXT: SD killed renamable $x11, killed $x12, 48 :: (store (s64) into %ir.3)
     ; CHECK-NEXT: PseudoRET
Index: llvm/lib/Target/RISCV/RISCVMakeCompressible.cpp
===================================================================
--- llvm/lib/Target/RISCV/RISCVMakeCompressible.cpp
+++ llvm/lib/Target/RISCV/RISCVMakeCompressible.cpp
@@ -293,8 +293,16 @@
   assert((isCompressibleLoad(MI) || isCompressibleStore(MI)) &&
          "Unsupported instruction for this optimization.");
 
+  int SkipN = 0;
+
+  // Skip the first (value) operand to a store instruction (except if the store
+  // offset is zero) in order to avoid an incorrect transformation.
+  // e.g. sd a0, 808(a0) to addi a2, a0, 768; sd a2, 40(a2)
+  if (isCompressibleStore(MI) && OldRegImm.Imm != 0)
+    SkipN = 1;
+
   // Update registers
-  for (MachineOperand &MO : MI.operands())
+  for (MachineOperand &MO : drop_begin(MI.operands(), SkipN))
     if (MO.isReg() && MO.getReg() == OldRegImm.Reg) {
       // Do not update operands that define the old register.
       //


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