[PATCH] D46797: [X86DomainReassignment] Don't delete IMPLICIT_DEF nodes

[Keno Fischer via Phabricator via llvm-commits]

loladiro created this revision.
loladiro added reviewers: craig.topper, guyblank.

We cannot simply delete IMPLICIT_DEF nodes. They may be used
later (e.g. by a PHI) and deleting them will cause later passes (e.g.
LiveVariables) to crash. However, it seems fine to ignore them for
purposes of the domain reassignment (as we do with PHI).

Fixes PR37430
Fixes JuliaLang/julia#27080


Repository:
  rL LLVM

https://reviews.llvm.org/D46797

Files:
  lib/Target/X86/X86DomainReassignment.cpp
  test/CodeGen/X86/domain-reassignment-implicit-def.ll


Index: test/CodeGen/X86/domain-reassignment-implicit-def.ll
===================================================================
--- /dev/null
+++ test/CodeGen/X86/domain-reassignment-implicit-def.ll
@@ -0,0 +1,25 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mcpu=skylake-avx512 -mtriple=x86_64-unknown-linux-gnu %s -o - | FileCheck %s
+
+; Check that the X86 Domain Reassignment pass doesn't drop IMPLICIT_DEF nodes,
+; which would later cause crashes (e.g. in LiveVariables) - see PR37430
+define void @domain_reassignment_implicit_def(i1 %cond, i8 *%mem, float %arg) {
+; CHECK:    vxorps %xmm1, %xmm1, %xmm1
+; CHECK:    vcmpneqss %xmm1, %xmm0, %k0
+; CHECK:    kmovb %k0, (%rsi)
+top:
+  br i1 %cond, label %L19, label %L15
+
+L15:                                              ; preds = %top
+  %tmp47 = fcmp une float 0.000000e+00, %arg
+  %tmp48 = zext i1 %tmp47 to i8
+  br label %L21
+
+L19:                                              ; preds = %top
+  br label %L21
+
+L21:                                              ; preds = %L19, %L15
+  %.sroa.0.0 = phi i8 [ undef, %L19 ], [ %tmp48, %L15 ]
+  store i8 %.sroa.0.0, i8* %mem, align 1
+  ret void
+}
Index: lib/Target/X86/X86DomainReassignment.cpp
===================================================================
--- lib/Target/X86/X86DomainReassignment.cpp
+++ lib/Target/X86/X86DomainReassignment.cpp
@@ -262,25 +262,6 @@
   }
 };
 
-/// An Instruction Converter which completely deletes an instruction.
-/// For example, IMPLICIT_DEF instructions can be deleted when converting from
-/// GPR to mask.
-class InstrDeleter : public InstrConverterBase {
-public:
-  InstrDeleter(unsigned SrcOpcode) : InstrConverterBase(SrcOpcode) {}
-
-  bool convertInstr(MachineInstr *MI, const TargetInstrInfo *TII,
-                    MachineRegisterInfo *MRI) const override {
-    assert(isLegal(MI, TII) && "Cannot convert instruction");
-    return true;
-  }
-
-  double getExtraCost(const MachineInstr *MI,
-                      MachineRegisterInfo *MRI) const override {
-    return 0;
-  }
-};
-
 // Key type to be used by the Instruction Converters map.
 // A converter is identified by <destination domain, source opcode>
 typedef std::pair<int, unsigned> InstrConverterBaseKeyTy;
@@ -587,7 +568,7 @@
       new InstrIgnore(TargetOpcode::PHI);
 
   Converters[{MaskDomain, TargetOpcode::IMPLICIT_DEF}] =
-      new InstrDeleter(TargetOpcode::IMPLICIT_DEF);
+      new InstrIgnore(TargetOpcode::IMPLICIT_DEF);
 
   Converters[{MaskDomain, TargetOpcode::INSERT_SUBREG}] =
       new InstrReplaceWithCopy(TargetOpcode::INSERT_SUBREG, 2);


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