CodeGen: check return types match when emitting tail call to builtin.

We were just completely ignoring the types when determining whether we could
safely emit a libcall as a tail call. This is clearly wrong.

Theoretically, we could dig deeper looking for incidental matches (much like
the generic code in Analysis.cpp does), but it's probably not worth it for the
few libcalls that exist.

llvm-svn: 264084

llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

@@ -2247,9 +2247,12 @@ SDValue SelectionDAGLegalize::ExpandLibCall(RTLIB::Libcall LC, SDNode *Node,
   SDValue InChain = DAG.getEntryNode();
 
   // isTailCall may be true since the callee does not reference caller stack
-  // frame. Check if it's in the right position.
+  // frame. Check if it's in the right position and that the return types match.
   SDValue TCChain = InChain;
-  bool isTailCall = TLI.isInTailCallPosition(DAG, Node, TCChain);
+  const Function *F = DAG.getMachineFunction().getFunction();
+  bool isTailCall =
+      TLI.isInTailCallPosition(DAG, Node, TCChain) &&
+      (RetTy == F->getReturnType() || F->getReturnType()->isVoidTy());
   if (isTailCall)
     InChain = TCChain;
 

llvm/test/CodeGen/ARM/tail-call-builtin.ll

@@ -0,0 +1,37 @@
+; RUN: llc -mtriple=thumbv7-linux-gnueabihf %s -o - | FileCheck %s
+
+define i64 @test_mismatched_call(double %in) {
+; CHECK-LABEL: test_mismatched_call:
+; CHECK: bl floor
+; CHECK: vmov r0, r1, d0
+
+  %val = tail call double @floor(double %in)
+  %res = bitcast double %val to i64
+  ret i64 %res
+}
+
+define double @test_matched_call(double %in) {
+; CHECK-LABEL: test_matched_call:
+; CHECK: b floor
+
+  %val = tail call double @floor(double %in)
+  ret double %val
+}
+
+define void @test_irrelevant_call(double %in) {
+; CHECK-LABEL: test_irrelevant_call:
+; CHECK-NOT: bl floor
+
+  %val = tail call double @floor(double %in)
+  ret void
+}
+
+define arm_aapcscc double @test_callingconv(double %in) {
+; CHECK: test_callingconv:
+; CHECK: bl floor
+
+  %val = tail call double @floor(double %in)
+  ret double %val
+}
+
+declare double @floor(double) nounwind readonly

llvm/test/CodeGen/X86/atomic-non-integer.ll

@@ -43,7 +43,7 @@ define half @load_half(half* %fptr) {
 ; CHECK-LABEL: @load_half
 ; CHECK: movw	(%rdi), %ax
 ; CHECK: movzwl	%ax, %edi
-; CHECK: jmp	__gnu_h2f_ieee
+; CHECK: callq	__gnu_h2f_ieee
   %v = load atomic half, half* %fptr unordered, align 2
   ret half %v
 }