[llvm] 4a0c89a - [WebAssembly] Fix fixBrTableIndex removing instruction without checking uses

[Wouter van Oortmerssen via llvm-commits]

Author: Wouter van Oortmerssen
Date: 2021-11-08T15:53:44-08:00
New Revision: 4a0c89a6cf8f368583f9c0724dbcb04fb17204ec

URL: https://github.com/llvm/llvm-project/commit/4a0c89a6cf8f368583f9c0724dbcb04fb17204ec
DIFF: https://github.com/llvm/llvm-project/commit/4a0c89a6cf8f368583f9c0724dbcb04fb17204ec.diff

LOG: [WebAssembly] Fix fixBrTableIndex removing instruction without checking uses

Fixes: https://bugs.llvm.org/show_bug.cgi?id=52352
Differential Revision: https://reviews.llvm.org/D113230

Added: 
    

Modified: 
    llvm/lib/Target/WebAssembly/WebAssemblyFixBrTableDefaults.cpp

Removed: 
    


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diff  --git a/llvm/lib/Target/WebAssembly/WebAssemblyFixBrTableDefaults.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyFixBrTableDefaults.cpp
index 52aa3534c78ef..5bdec89f1125f 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyFixBrTableDefaults.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyFixBrTableDefaults.cpp
@@ -61,9 +61,13 @@ void fixBrTableIndex(MachineInstr &MI, MachineBasicBlock *MBB,
   auto ExtMI = MF.getRegInfo().getVRegDef(MI.getOperand(0).getReg());
   if (ExtMI->getOpcode() == WebAssembly::I64_EXTEND_U_I32) {
     // Unnecessarily extending a 32-bit value to 64, remove it.
-    assert(MI.getOperand(0).getReg() == ExtMI->getOperand(0).getReg());
+    auto ExtDefReg = ExtMI->getOperand(0).getReg();
+    assert(MI.getOperand(0).getReg() == ExtDefReg);
     MI.getOperand(0).setReg(ExtMI->getOperand(1).getReg());
-    ExtMI->eraseFromParent();
+    if (MF.getRegInfo().use_nodbg_empty(ExtDefReg)) {
+      // No more users of extend, delete it.
+      ExtMI->eraseFromParent();
+    }
   } else {
     // Incoming 64-bit value that needs to be truncated.
     Register Reg32 =