[llvm] r245106 - [msan] Fix handling of musttail calls.

[Evgeniy Stepanov via llvm-commits]

Author: eugenis
Date: Fri Aug 14 17:03:50 2015
New Revision: 245106

URL: http://llvm.org/viewvc/llvm-project?rev=245106&view=rev
Log:
[msan] Fix handling of musttail calls.

MSan instrumentation for return values of musttail calls is not
allowed by the IR constraints, and not needed at the same time.

Modified:
    llvm/trunk/lib/Transforms/Instrumentation/MemorySanitizer.cpp
    llvm/trunk/test/Instrumentation/MemorySanitizer/msan_basic.ll

Modified: llvm/trunk/lib/Transforms/Instrumentation/MemorySanitizer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/MemorySanitizer.cpp?rev=245106&r1=245105&r2=245106&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Instrumentation/MemorySanitizer.cpp (original)
+++ llvm/trunk/lib/Transforms/Instrumentation/MemorySanitizer.cpp Fri Aug 14 17:03:50 2015
@@ -1339,6 +1339,12 @@ struct MemorySanitizerVisitor : public I
   }
 
   void visitBitCastInst(BitCastInst &I) {
+    // Special case: if this is the bitcast (there is exactly 1 allowed) between
+    // a musttail call and a ret, don't instrument. New instructions are not
+    // allowed after a musttail call.
+    if (auto *CI = dyn_cast<CallInst>(I.getOperand(0)))
+      if (CI->isMustTailCall())
+        return;
     IRBuilder<> IRB(&I);
     setShadow(&I, IRB.CreateBitCast(getShadow(&I, 0), getShadowTy(&I)));
     setOrigin(&I, getOrigin(&I, 0));
@@ -2493,6 +2499,8 @@ struct MemorySanitizerVisitor : public I
 
     // Now, get the shadow for the RetVal.
     if (!I.getType()->isSized()) return;
+    // Don't emit the epilogue for musttail call returns.
+    if (CS.isCall() && cast<CallInst>(&I)->isMustTailCall()) return;
     IRBuilder<> IRBBefore(&I);
     // Until we have full dynamic coverage, make sure the retval shadow is 0.
     Value *Base = getShadowPtrForRetval(&I, IRBBefore);
@@ -2523,10 +2531,22 @@ struct MemorySanitizerVisitor : public I
       setOrigin(&I, IRBAfter.CreateLoad(getOriginPtrForRetval(IRBAfter)));
   }
 
+  bool isAMustTailRetVal(Value *RetVal) {
+    if (auto *I = dyn_cast<BitCastInst>(RetVal)) {
+      RetVal = I->getOperand(0);
+    }
+    if (auto *I = dyn_cast<CallInst>(RetVal)) {
+      return I->isMustTailCall();
+    }
+    return false;
+  }
+
   void visitReturnInst(ReturnInst &I) {
     IRBuilder<> IRB(&I);
     Value *RetVal = I.getReturnValue();
     if (!RetVal) return;
+    // Don't emit the epilogue for musttail call returns.
+    if (isAMustTailRetVal(RetVal)) return;
     Value *ShadowPtr = getShadowPtrForRetval(RetVal, IRB);
     if (CheckReturnValue) {
       insertShadowCheck(RetVal, &I);

Modified: llvm/trunk/test/Instrumentation/MemorySanitizer/msan_basic.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Instrumentation/MemorySanitizer/msan_basic.ll?rev=245106&r1=245105&r2=245106&view=diff
==============================================================================
--- llvm/trunk/test/Instrumentation/MemorySanitizer/msan_basic.ll (original)
+++ llvm/trunk/test/Instrumentation/MemorySanitizer/msan_basic.ll Fri Aug 14 17:03:50 2015
@@ -864,6 +864,7 @@ entry:
 ; CHECK: call void (i32, ...) @VAArgStructFn
 ; CHECK: ret void
 
+
 declare i32 @InnerTailCall(i32 %a)
 
 define void @MismatchedReturnTypeTailCall(i32 %a) sanitize_memory {
@@ -878,5 +879,41 @@ define void @MismatchedReturnTypeTailCal
 ; CHECK: tail call i32 @InnerTailCall
 ; CHECK: ret void
 
+
+declare i32 @MustTailCall(i32 %a)
+
+define i32 @CallMustTailCall(i32 %a) sanitize_memory {
+  %b = musttail call i32 @MustTailCall(i32 %a)
+  ret i32 %b
+}
+
+; For "musttail" calls we can not insert any shadow manipulating code between
+; call and the return instruction. And we don't need to, because everything is
+; taken care of in the callee.
+
+; CHECK-LABEL: define i32 @CallMustTailCall
+; CHECK: musttail call i32 @MustTailCall
+; No instrumentation between call and ret.
+; CHECK-NEXT: ret i32
+
+declare i32* @MismatchingMustTailCall(i32 %a)
+
+define i8* @MismatchingCallMustTailCall(i32 %a) sanitize_memory {
+  %b = musttail call i32* @MismatchingMustTailCall(i32 %a)
+  %c = bitcast i32* %b to i8*
+  ret i8* %c
+}
+
+; For "musttail" calls we can not insert any shadow manipulating code between
+; call and the return instruction. And we don't need to, because everything is
+; taken care of in the callee.
+
+; CHECK-LABEL: define i8* @MismatchingCallMustTailCall
+; CHECK: musttail call i32* @MismatchingMustTailCall
+; No instrumentation between call and ret.
+; CHECK-NEXT: bitcast i32* {{.*}} to i8*
+; CHECK-NEXT: ret i8*
+
+
 ; CHECK-LABEL: define internal void @msan.module_ctor
 ; CHECK: call void @__msan_init()