Fix an issue with certain constants as live values in patchpoints.

[sanjoy]

Summary

The patchpoint lowering logic crashes with live constants equal to the tombstone or empty keys of a DenseMap<uint64_t, T>. This patch fixes the issue (and adds a tests case).

[ributzka]

LGTM

lib/CodeGen/StackMaps.cpp

225

uint64_ts -> 'uint64_t's

230

Maybe we should add an assert here to make sure this won't happen in the future.

[atrick]

Thanks! Good idea Juergen.
-Andy

include/llvm/CodeGen/StackMaps.h

public:
   /// afterwards.
   void serializeToStackMapSection();
 
 private:
   static const char *WSMP;
 
   typedef SmallVector<Location, 8> LocationVec;
   typedef SmallVector<LiveOutReg, 8> LiveOutVec;
-  typedef MapVector<int64_t, int64_t> ConstantPool;
+  typedef MapVector<uint64_t, uint64_t> ConstantPool;
   typedef MapVector<const MCSymbol *, uint64_t> FnStackSizeMap;
 
   struct CallsiteInfo {
     const MCExpr *CSOffsetExpr;
     uint64_t ID;
     LocationVec Locations;
     LiveOutVec LiveOuts;
     CallsiteInfo() : CSOffsetExpr(nullptr), ID(0) {}

lib/CodeGen/StackMaps.cpp

void StackMaps::recordStackMapOpers(const MachineInstr &MI, uint64_t ID,
 
   // Move large constants into the constant pool.
   for (LocationVec::iterator I = Locations.begin(), E = Locations.end();
        I != E; ++I) {
     // Constants are encoded as sign-extended integers.
     // -1 is directly encoded as .long 0xFFFFFFFF with no constant pool.
     if (I->LocType == Location::Constant && !isInt<32>(I->Offset)) {
       I->LocType = Location::ConstantIndex;
+      // ConstPool is intentionally a MapVector of uint64_ts (as
+      // opposed to int64_ts).  We should never be in a situation
+      // where we have to insert either the tombstone or the empty
+      // keys into a map, and for a DenseMap<uint64_t, T> these are
+      // (uint64_t)0 and (uint64_t)-1.  They can be and are
+      // represented using 32 bit integers.
       auto Result = ConstPool.insert(std::make_pair(I->Offset, I->Offset));
       I->Offset = Result.first - ConstPool.begin();
     }
   }
 
   // Create an expression to calculate the offset of the callsite from function
   // entry.
   const MCExpr *CSOffsetExpr = MCBinaryExpr::CreateSub(

test/CodeGen/X86/stackmap-large-constants.ll

+; RUN: llc < %s -mtriple=x86_64-apple-darwin | FileCheck %s
+
+; CHECK-LABEL:  .section  __LLVM_STACKMAPS,__llvm_stackmaps
+; CHECK-NEXT: __LLVM_StackMaps:
+; version
+; CHECK-NEXT:   .byte 1
+; reserved
+; CHECK-NEXT:   .byte 0
+; reserved
+; CHECK-NEXT:   .short  0
+; # functions
+; CHECK-NEXT:   .long 2
+; # constants
+; CHECK-NEXT:   .long 2
+; # records
+; CHECK-NEXT:   .long 2
+; function address & stack size
+; CHECK-NEXT:   .quad _foo
+; CHECK-NEXT:   .quad 8
+; function address & stack size
+; CHECK-NEXT:   .quad _bar
+; CHECK-NEXT:   .quad 8
+
+; Constants Array:
+; CHECK-NEXT:   .quad 9223372036854775807
+; CHECK-NEXT:   .quad -9223372036854775808
+
+; Patchpoint ID
+; CHECK-NEXT:   .quad 0
+; Instruction offset
+; CHECK-NEXT:   .long Ltmp3-_foo
+; reserved
+; CHECK-NEXT:   .short  0
+; # locations
+; CHECK-NEXT:   .short  1
+; ConstantIndex
+; CHECK-NEXT:   .byte 5
+; reserved
+; CHECK-NEXT:   .byte 8
+; Dwarf RegNum
+; CHECK-NEXT:   .short  0
+; Offset
+; CHECK-NEXT:   .long 0
+; padding
+; CHECK-NEXT:   .short  0
+; NumLiveOuts
+; CHECK-NEXT:   .short  0
+
+; CHECK-NEXT:   .align  3
+
+declare void @llvm.experimental.stackmap(i64, i32, ...)
+
+define void @foo() {
+  tail call void (i64, i32, ...)* @llvm.experimental.stackmap(i64 0, i32 0, i64 9223372036854775807)
+  ret void
+}
+
+; Patchpoint ID
+; CHECK-NEXT:   .quad 0
+; Instruction Offset
+; CHECK-NEXT:   .long Ltmp7-_bar
+; reserved
+; CHECK-NEXT:   .short  0
+; # locations
+; CHECK-NEXT:   .short  1
+; ConstantIndex
+; CHECK-NEXT:   .byte 5
+; reserved
+; CHECK-NEXT:   .byte 8
+; Dwarf RegNum
+; CHECK-NEXT:   .short  0
+; Offset
+; CHECK-NEXT:   .long 1
+; padding
+; CHECK-NEXT:   .short  0
+; NumLiveOuts
+; CHECK-NEXT:   .short  0
+
+
+define void @bar() {
+  tail call void (i64, i32, ...)* @llvm.experimental.stackmap(i64 0, i32 0, i64 -9223372036854775808)
+  ret void
+}