[AMDGPU] Fixed asan failure in SIFoldOperands

Both tryFoldOMod() and tryFoldClamp() remove original instruction,
so the check MI.modifiesRegister() may use a deleted MI.

Differential Revision: https://reviews.llvm.org/D69448

diff --git a/llvm/lib/Target/AMDGPU/SIFoldOperands.cpp b/llvm/lib/Target/AMDGPU/SIFoldOperands.cpp
index a141a22..f24510b 100644 (file)
--- a/llvm/lib/Target/AMDGPU/SIFoldOperands.cpp
+++ b/llvm/lib/Target/AMDGPU/SIFoldOperands.cpp
@@ -1468,15 +1468,16 @@ bool SIFoldOperands::runOnMachineFunction(MachineFunction &MF) {
       tryFoldInst(TII, &MI);
 
       if (!TII->isFoldableCopy(MI)) {
+        // Saw an unknown clobber of m0, so we no longer know what it is.
+        if (CurrentKnownM0Val && MI.modifiesRegister(AMDGPU::M0, TRI))
+          CurrentKnownM0Val = nullptr;
+
         // TODO: Omod might be OK if there is NSZ only on the source
         // instruction, and not the omod multiply.
         if (IsIEEEMode || (!HasNSZ && !MI.getFlag(MachineInstr::FmNsz)) ||
             !tryFoldOMod(MI))
           tryFoldClamp(MI);
 
-        // Saw an unknown clobber of m0, so we no longer know what it is.
-        if (CurrentKnownM0Val && MI.modifiesRegister(AMDGPU::M0, TRI))
-          CurrentKnownM0Val = nullptr;
         continue;
       }