[llvm] e95fc20 - [X86] getFMA3OpcodeToCommuteOperands - use unreachable to detect fma3 format mismatch

[Simon Pilgrim via llvm-commits]

Author: Simon Pilgrim
Date: 2022-02-10T17:14:39Z
New Revision: e95fc20f0463a27288407a4b67a7d71084666134

URL: https://github.com/llvm/llvm-project/commit/e95fc20f0463a27288407a4b67a7d71084666134
DIFF: https://github.com/llvm/llvm-project/commit/e95fc20f0463a27288407a4b67a7d71084666134.diff

LOG: [X86] getFMA3OpcodeToCommuteOperands - use unreachable to detect fma3 format mismatch

Matches what we do in getThreeSrcCommuteCase.

Fixes static analyzer out of bounds array access warning.

Added: 
    

Modified: 
    llvm/lib/Target/X86/X86InstrInfo.cpp

Removed: 
    


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diff  --git a/llvm/lib/Target/X86/X86InstrInfo.cpp b/llvm/lib/Target/X86/X86InstrInfo.cpp
index 4dcd886fa3b2..d2b422172511 100644
--- a/llvm/lib/Target/X86/X86InstrInfo.cpp
+++ b/llvm/lib/Target/X86/X86InstrInfo.cpp
@@ -1957,14 +1957,13 @@ unsigned X86InstrInfo::getFMA3OpcodeToCommuteOperands(
   FMAForms[0] = FMA3Group.get132Opcode();
   FMAForms[1] = FMA3Group.get213Opcode();
   FMAForms[2] = FMA3Group.get231Opcode();
-  unsigned FormIndex;
-  for (FormIndex = 0; FormIndex < 3; FormIndex++)
-    if (Opc == FMAForms[FormIndex])
-      break;
 
   // Everything is ready, just adjust the FMA opcode and return it.
-  FormIndex = FormMapping[Case][FormIndex];
-  return FMAForms[FormIndex];
+  for (unsigned FormIndex = 0; FormIndex < 3; FormIndex++)
+    if (Opc == FMAForms[FormIndex])
+      return FMAForms[FormMapping[Case][FormIndex]];
+
+  llvm_unreachable("Illegal FMA3 format");
 }
 
 static void commuteVPTERNLOG(MachineInstr &MI, unsigned SrcOpIdx1,