[llvm] r208912 - Don't insert lifetime.end markers between a musttail call and ret

[Reid Kleckner]

Author: rnk
Date: Thu May 15 15:39:13 2014
New Revision: 208912

URL: http://llvm.org/viewvc/llvm-project?rev=208912&view=rev
Log:
Don't insert lifetime.end markers between a musttail call and ret

The allocas going out of scope are immediately killed by the return
instruction.

Reviewers: chandlerc

Differential Revision: http://reviews.llvm.org/D3630

Modified:
    llvm/trunk/lib/Transforms/Utils/InlineFunction.cpp
    llvm/trunk/test/Transforms/Inline/inline-tail.ll

Modified: llvm/trunk/lib/Transforms/Utils/InlineFunction.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/InlineFunction.cpp?rev=208912&r1=208911&r2=208912&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/InlineFunction.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/InlineFunction.cpp Thu May 15 15:39:13 2014
@@ -758,8 +758,13 @@ bool llvm::InlineFunction(CallSite CS, I
       }
 
       builder.CreateLifetimeStart(AI, AllocaSize);
-      for (ReturnInst *RI : Returns)
+      for (ReturnInst *RI : Returns) {
+        // Don't insert llvm.lifetime.end calls between a musttail call and a
+        // return.  The return kills all local allocas.
+        if (InlinedMustTailCalls && getPrecedingMustTailCall(RI))
+          continue;
         IRBuilder<>(RI).CreateLifetimeEnd(AI, AllocaSize);
+      }
     }
   }
 
@@ -777,8 +782,13 @@ bool llvm::InlineFunction(CallSite CS, I
 
     // Insert a call to llvm.stackrestore before any return instructions in the
     // inlined function.
-    for (ReturnInst *RI : Returns)
+    for (ReturnInst *RI : Returns) {
+      // Don't insert llvm.stackrestore calls between a musttail call and a
+      // return.  The return will restore the stack pointer.
+      if (InlinedMustTailCalls && getPrecedingMustTailCall(RI))
+        continue;
       IRBuilder<>(RI).CreateCall(StackRestore, SavedPtr);
+    }
   }
 
   // If we are inlining for an invoke instruction, we must make sure to rewrite

Modified: llvm/trunk/test/Transforms/Inline/inline-tail.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/Inline/inline-tail.ll?rev=208912&r1=208911&r2=208912&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/Inline/inline-tail.ll (original)
+++ llvm/trunk/test/Transforms/Inline/inline-tail.ll Thu May 15 15:39:13 2014
@@ -49,6 +49,42 @@ define void @test_musttail_basic_a(i32*
   ret void
 }
 
+; Don't insert lifetime end markers here, the lifetime is trivially over due
+; the return.
+; CHECK: define void @test_byval_a(
+; CHECK: musttail call void @test_byval_c(
+; CHECK-NEXT: ret void
+
+declare void @test_byval_c(i32* byval %p)
+define internal void @test_byval_b(i32* byval %p) {
+  musttail call void @test_byval_c(i32* byval %p)
+  ret void
+}
+define void @test_byval_a(i32* byval %p) {
+  musttail call void @test_byval_b(i32* byval %p)
+  ret void
+}
+
+; Don't insert a stack restore, we're about to return.
+; CHECK: define void @test_dynalloca_a(
+; CHECK: call i8* @llvm.stacksave(
+; CHECK: alloca i8, i32 %n
+; CHECK: musttail call void @test_dynalloca_c(
+; CHECK-NEXT: ret void
+
+declare void @escape(i8* %buf)
+declare void @test_dynalloca_c(i32* byval %p, i32 %n)
+define internal void @test_dynalloca_b(i32* byval %p, i32 %n) alwaysinline {
+  %buf = alloca i8, i32 %n              ; dynamic alloca
+  call void @escape(i8* %buf)           ; escape it
+  musttail call void @test_dynalloca_c(i32* byval %p, i32 %n)
+  ret void
+}
+define void @test_dynalloca_a(i32* byval %p, i32 %n) {
+  musttail call void @test_dynalloca_b(i32* byval %p, i32 %n)
+  ret void
+}
+
 ; We can't merge the returns.
 ; CHECK: define void @test_multiret_a(
 ; CHECK: musttail call void @test_multiret_c(