[inlineasm] Fix crash when number of matched input constraint operands overflows signed char

[dfukalov]

Summary

In a case when number of output constraint operands that has matched input operands
doesn't fit to signed char, TargetLowering::ParseConstraints() can try to access
ConstraintOperands (that is std::vector) with negative index.

[rampitec]

test/CodeGen/AMDGPU/InlineAsmCrash.ll

2

Please add -verify-machineinstrs

[hfinkel]

Please post this patch with full context.

[dfukalov]

Sorry for incomplete diff

[arsenm]

LGTM with the minor cleanups

lib/IR/InlineAsm.cpp

166

Spaces around >=

174

Ditto

test/CodeGen/AMDGPU/InlineAsmCrash.ll

2

This should check something in the output

include/llvm/IR/InlineAsm.h

public:
 
   using ConstraintCodeVector = std::vector<std::string>;
 
   struct SubConstraintInfo {
     /// MatchingInput - If this is not -1, this is an output constraint where an
     /// input constraint is required to match it (e.g. "0").  The value is the
     /// constraint number that matches this one (for example, if this is
     /// constraint #0 and constraint #4 has the value "0", this will be 4).
-    signed char MatchingInput = -1;
+    int MatchingInput = -1;
 
     /// Code - The constraint code, either the register name (in braces) or the
     /// constraint letter/number.
     ConstraintCodeVector Codes;
 
     /// Default constructor.
     SubConstraintInfo() = default;
   };
struct ConstraintInfo {
     /// isEarlyClobber - "&": output operand writes result before inputs are all
     /// read.  This is only ever set for an output operand.
     bool isEarlyClobber = false;
 
     /// MatchingInput - If this is not -1, this is an output constraint where an
     /// input constraint is required to match it (e.g. "0").  The value is the
     /// constraint number that matches this one (for example, if this is
     /// constraint #0 and constraint #4 has the value "0", this will be 4).
-    signed char MatchingInput = -1;
+    int MatchingInput = -1;
 
     /// hasMatchingInput - Return true if this is an output constraint that has
     /// a matching input constraint.
     bool hasMatchingInput() const { return MatchingInput != -1; }
 
     /// isCommutative - This is set to true for a constraint that is commutative
     /// with the next operand.
     bool isCommutative = false;

lib/IR/InlineAsm.cpp

if (*I == '{') {   // Physical register reference.
             ConstraintsSoFar[N].multipleAlternatives.size())
           return true;
         InlineAsm::SubConstraintInfo &scInfo =
           ConstraintsSoFar[N].multipleAlternatives[multipleAlternativeIndex];
         if (scInfo.MatchingInput != -1)
           return true;
         // Note that operand #n has a matching input.
         scInfo.MatchingInput = ConstraintsSoFar.size();
+        assert(scInfo.MatchingInput>=0);
       } else {
         if (ConstraintsSoFar[N].hasMatchingInput() &&
             (size_t)ConstraintsSoFar[N].MatchingInput !=
                 ConstraintsSoFar.size())
           return true;
         // Note that operand #n has a matching input.
         ConstraintsSoFar[N].MatchingInput = ConstraintsSoFar.size();
+        assert(ConstraintsSoFar[N].MatchingInput>=0);
         }
     } else if (*I == '|') {
       multipleAlternativeIndex++;
       pCodes = &multipleAlternatives[multipleAlternativeIndex].Codes;
       ++I;
     } else if (*I == '^') {
       // Multi-letter constraint
       // FIXME: For now assuming these are 2-character constraints.

test/CodeGen/AMDGPU/InlineAsmCrash.ll

+; RUN: llc -march=amdgcn < %s
+
+define void @foo(i32* %ptr) {
+  %tmp = tail call { i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32 } asm "nop", "=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,=v,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65"(i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2)
+  %tmp2 = extractvalue { i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32 } %tmp, 0
+  store i32 %tmp2, i32* %ptr, align 4
+  ret void
+}