[PATCH] D97792: BPF: Fix a bug in peephole TRUNC elimination optimization

[Yonghong Song 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 rG51cdb780db3b: BPF: Fix a bug in peephole TRUNC elimination optimization (authored by yonghong-song).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D97792/new/

https://reviews.llvm.org/D97792

Files:
  llvm/lib/Target/BPF/BPFMIPeephole.cpp
  llvm/test/CodeGen/BPF/remove_truncate_8.ll


Index: llvm/test/CodeGen/BPF/remove_truncate_8.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/BPF/remove_truncate_8.ll
@@ -0,0 +1,41 @@
+; RUN: llc < %s -march=bpf -verify-machineinstrs | FileCheck %s
+; Source Code:
+;   struct loc_prog {
+;     unsigned int ip;
+;     int len;
+;   };
+;   int exec_prog(struct loc_prog *prog) {
+;     if (prog->ip < prog->len) {
+;       int x = prog->ip;
+;       if (x < 3)
+;         prog->ip += 2;
+;     }
+;     return 3;
+;   }
+; Compilation flag:
+;   clang -target bpf -O2 -S -emit-llvm t.c
+
+%struct.loc_prog = type { i32, i32 }
+
+; Function Attrs: nofree norecurse nounwind willreturn
+define dso_local i32 @exec_prog(%struct.loc_prog* nocapture %prog) local_unnamed_addr {
+entry:
+  %ip = getelementptr inbounds %struct.loc_prog, %struct.loc_prog* %prog, i64 0, i32 0
+  %0 = load i32, i32* %ip, align 4
+  %len = getelementptr inbounds %struct.loc_prog, %struct.loc_prog* %prog, i64 0, i32 1
+  %1 = load i32, i32* %len, align 4
+  %cmp = icmp ult i32 %0, %1
+  %cmp2 = icmp slt i32 %0, 3
+  %or.cond = and i1 %cmp2, %cmp
+; CHECK: r{{[0-9]+}} <<= 32
+; CHECK: r{{[0-9]+}} s>>= 32
+  br i1 %or.cond, label %if.then3, label %if.end5
+
+if.then3:                                         ; preds = %entry
+  %add = add nsw i32 %0, 2
+  store i32 %add, i32* %ip, align 4
+  br label %if.end5
+
+if.end5:                                          ; preds = %if.then3, %entry
+  ret i32 3
+}
Index: llvm/lib/Target/BPF/BPFMIPeephole.cpp
===================================================================
--- llvm/lib/Target/BPF/BPFMIPeephole.cpp
+++ llvm/lib/Target/BPF/BPFMIPeephole.cpp
@@ -475,6 +475,9 @@
       if (MI.getOpcode() == BPF::SRL_ri &&
           MI.getOperand(2).getImm() == 32) {
         SrcReg = MI.getOperand(1).getReg();
+        if (!MRI->hasOneNonDBGUse(SrcReg))
+          continue;
+
         MI2 = MRI->getVRegDef(SrcReg);
         DstReg = MI.getOperand(0).getReg();
 


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