Make instcombine promote inline asm calls to 'nounwind'

calls.  Remove special casing of inline asm from the
inliner.  There is a potential problem: the verifier
rejects invokes of inline asm (not sure why).  If an
asm call is not marked "nounwind" in some .ll, and
instcombine is not run, but the inliner is run, then
an illegal module will be created.  This is bad but
I'm not sure what the best approach is.  I'm tempted
to remove the check in the verifier...


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45073 91177308-0d34-0410-b5e6-96231b3b80d8

7 files changed, 35 insertions, 4 deletions

diff --git a/include/llvm/Support/CallSite.h b/include/llvm/Support/CallSite.h
index 5bb60a8a8a..3735842e72 100644
--- a/include/llvm/Support/CallSite.h
+++ b/include/llvm/Support/CallSite.h
@@ -73,6 +73,9 @@ public:
   /// @brief Determine if the call does not access or only reads memory.
   bool onlyReadsMemory() const;
 
+  /// @brief Determine if the call cannot unwind.
+  bool isNoUnwind() const;
+
   /// getType - Return the type of the instruction that generated this call site
   ///
   const Type *getType() const { return I->getType(); }
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 653d35e34f..aa9e932fc5 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -7972,6 +7972,19 @@ Instruction *InstCombiner::visitCallSite(CallSite CS) {
       }
   }
 
+  if (isa<InlineAsm>(Callee) && !CS.isNoUnwind()) {
+    // Inline asm calls cannot throw - mark them 'nounwind'.
+    const ParamAttrsList *PAL = CS.getParamAttrs();
+    uint16_t RAttributes = PAL ? PAL->getParamAttrs(0) : 0;
+    RAttributes |= ParamAttr::NoUnwind;
+
+    ParamAttrsVector modVec;
+    modVec.push_back(ParamAttrsWithIndex::get(0, RAttributes));
+    PAL = ParamAttrsList::getModified(PAL, modVec);
+    CS.setParamAttrs(PAL);
+    Changed = true;
+  }
+
   return Changed ? CS.getInstruction() : 0;
 }
 
diff --git a/lib/Transforms/Utils/InlineFunction.cpp b/lib/Transforms/Utils/InlineFunction.cpp
index e9f6b28e98..3d31f71300 100644
--- a/lib/Transforms/Utils/InlineFunction.cpp
+++ b/lib/Transforms/Utils/InlineFunction.cpp
@@ -69,9 +69,8 @@ static void HandleInlinedInvoke(InvokeInst *II, BasicBlock *FirstNewBlock,
           if (!isa<CallInst>(I)) continue;
           CallInst *CI = cast<CallInst>(I);
 
-          // If this call cannot unwind or is an inline asm, don't
-          // convert it to an invoke.
-          if (CI->isNoUnwind() || isa<InlineAsm>(CI->getCalledValue()))
+          // If this call cannot unwind, don't convert it to an invoke.
+          if (CI->isNoUnwind())
             continue;
 
           // Convert this function call into an invoke instruction.
diff --git a/lib/VMCore/Instructions.cpp b/lib/VMCore/Instructions.cpp
index 5207ea52f4..511a0e851a 100644
--- a/lib/VMCore/Instructions.cpp
+++ b/lib/VMCore/Instructions.cpp
@@ -65,6 +65,12 @@ bool CallSite::onlyReadsMemory() const {
   else
     return cast<InvokeInst>(I)->onlyReadsMemory();
 }
+bool CallSite::isNoUnwind() const {
+  if (CallInst *CI = dyn_cast<CallInst>(I))
+    return CI->isNoUnwind();
+  else
+    return cast<InvokeInst>(I)->isNoUnwind();
+}
 
 
 
diff --git a/test/CFrontend/2007-12-16-AsmNoUnwind.c b/test/CFrontend/2007-12-16-AsmNoUnwind.c
new file mode 100644
index 0000000000..b080e6a511
--- /dev/null
+++ b/test/CFrontend/2007-12-16-AsmNoUnwind.c
@@ -0,0 +1,3 @@
+// RUN: %llvmgcc %s -S -o - | grep nounwind
+
+void bar() { asm (""); }
diff --git a/test/Transforms/Inline/2007-04-15-InlineEH.ll b/test/Transforms/Inline/2007-04-15-InlineEH.ll
index 73b0e215e8..9d28755d28 100644
--- a/test/Transforms/Inline/2007-04-15-InlineEH.ll
+++ b/test/Transforms/Inline/2007-04-15-InlineEH.ll
@@ -8,7 +8,7 @@ target triple = "i686-pc-linux-gnu"
 
 define void @bc__support__high_resolution_time__clock() {
 entry:
-	call void asm "rdtsc\0A\09movl %eax, $0\0A\09movl %edx, $1", "=*imr,=*imr,~{dirflag},~{fpsr},~{flags},~{dx},~{ax}"( i32* null, i32* null )
+	call void asm "rdtsc\0A\09movl %eax, $0\0A\09movl %edx, $1", "=*imr,=*imr,~{dirflag},~{fpsr},~{flags},~{dx},~{ax}"( i32* null, i32* null ) nounwind
 	unreachable
 }
 
diff --git a/test/Transforms/InstCombine/2007-12-16-AsmNoUnwind.ll b/test/Transforms/InstCombine/2007-12-16-AsmNoUnwind.ll
new file mode 100644
index 0000000000..336c6d5a2e
--- /dev/null
+++ b/test/Transforms/InstCombine/2007-12-16-AsmNoUnwind.ll
@@ -0,0 +1,7 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep nounwind
+
+define void @bar() {
+entry:
+        call void asm sideeffect "", "~{dirflag},~{fpsr},~{flags}"( )
+        ret void
+}