[PATCH] D27864: AMDGPU: Don't add same instruction multiple times to worklist

[Matt Arsenault via Phabricator via llvm-commits]

arsenm created this revision.
arsenm added a subscriber: llvm-commits.
Herald added a reviewer: tstellarAMD.
Herald added subscribers: tony-tye, yaxunl, nhaehnle, wdng, kzhuravl.

When the instruction is processed the first time, it may be
deleted resulting in crashes. While the new test adds the same
user to the worklist twice, this particular case doesn't crash
but I'm not sure why.


https://reviews.llvm.org/D27864

Files:
  lib/Target/AMDGPU/SIInstrInfo.cpp
  test/CodeGen/AMDGPU/sminmax.ll


Index: test/CodeGen/AMDGPU/sminmax.ll
===================================================================
--- test/CodeGen/AMDGPU/sminmax.ll
+++ test/CodeGen/AMDGPU/sminmax.ll
@@ -32,6 +32,20 @@
   ret void
 }
 
+; GCN-LABEL: {{^}}v_abs_i32_repeat_user:
+; GCN: v_sub_i32_e32 [[NEG:v[0-9]+]], vcc, 0, [[SRC:v[0-9]+]]
+; GCN: v_max_i32_e32 [[MAX:v[0-9]+]], [[NEG]], [[SRC]]
+; GCN: v_mul_lo_i32 v{{[0-9]+}}, [[MAX]], [[MAX]]
+define void @v_abs_i32_repeat_user(i32 addrspace(1)* %out, i32 addrspace(1)* %src) nounwind {
+  %val = load i32, i32 addrspace(1)* %src, align 4
+  %neg = sub i32 0, %val
+  %cond = icmp sgt i32 %val, %neg
+  %res = select i1 %cond, i32 %val, i32 %neg
+  %mul = mul i32 %res, %res
+  store i32 %mul, i32 addrspace(1)* %out, align 4
+  ret void
+}
+
 ; FUNC-LABEL: {{^}}s_abs_v2i32:
 ; GCN: s_abs_i32
 ; GCN: s_abs_i32
Index: lib/Target/AMDGPU/SIInstrInfo.cpp
===================================================================
--- lib/Target/AMDGPU/SIInstrInfo.cpp
+++ lib/Target/AMDGPU/SIInstrInfo.cpp
@@ -3312,10 +3312,16 @@
   MachineRegisterInfo &MRI,
   SmallVectorImpl<MachineInstr *> &Worklist) const {
   for (MachineRegisterInfo::use_iterator I = MRI.use_begin(DstReg),
-         E = MRI.use_end(); I != E; ++I) {
+         E = MRI.use_end(); I != E;) {
     MachineInstr &UseMI = *I->getParent();
     if (!canReadVGPR(UseMI, I.getOperandNo())) {
       Worklist.push_back(&UseMI);
+
+      do {
+        ++I;
+      } while (I != E && I->getParent() == &UseMI);
+    } else {
+      ++I;
     }
   }
 }


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