[MIPS][ISel] Fix musttail

llvm/lib/Target/Mips/Mips16ISelLowering.cpp

@@ -247,8 +247,8 @@ Mips16TargetLowering::EmitInstrWithCustomInserter(MachineInstr &MI,
 }
 
 bool Mips16TargetLowering::isEligibleForTailCallOptimization(
-    const CCState &CCInfo, unsigned NextStackOffset,
-    const MipsFunctionInfo &FI) const {
+    const CCState &CCInfo, unsigned NextStackOffset, const MipsFunctionInfo &FI,
+    bool IsMustTail) const {
   // No tail call optimization for mips16.
   return false;
 }

llvm/lib/Target/Mips/Mips16ISelLowering.h

@@ -33,7 +33,7 @@ namespace llvm {
   private:
     bool isEligibleForTailCallOptimization(
         const CCState &CCInfo, unsigned NextStackOffset,
-        const MipsFunctionInfo &FI) const override;
+        const MipsFunctionInfo &FI, bool IsMustTail = false) const override;
 
     void setMips16HardFloatLibCalls();
 

llvm/lib/Target/Mips/MipsISelLowering.cpp

@@ -3407,18 +3407,22 @@ MipsTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
   // Check if it's really possible to do a tail call. Restrict it to functions
   // that are part of this compilation unit.
   bool InternalLinkage = false;
+  bool IsMustTail = CLI.CB && CLI.CB->isMustTailCall();
   if (IsTailCall) {
     IsTailCall = isEligibleForTailCallOptimization(
-        CCInfo, StackSize, *MF.getInfo<MipsFunctionInfo>());
-    if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee)) {
-      InternalLinkage = G->getGlobal()->hasInternalLinkage();
-      IsTailCall &= (InternalLinkage || G->getGlobal()->hasLocalLinkage() ||
-                     G->getGlobal()->hasPrivateLinkage() ||
-                     G->getGlobal()->hasHiddenVisibility() ||
-                     G->getGlobal()->hasProtectedVisibility());
-     }
+        CCInfo, StackSize, *MF.getInfo<MipsFunctionInfo>(), IsMustTail);
+    if (IsTailCall) {
+      if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee)) {
+        InternalLinkage = G->getGlobal()->hasInternalLinkage();
+        IsTailCall &= (InternalLinkage || G->getGlobal()->hasLocalLinkage() ||
+                       G->getGlobal()->isDSOLocal() ||
+                       G->getGlobal()->hasPrivateLinkage() ||
+                       G->getGlobal()->hasHiddenVisibility() ||
+                       G->getGlobal()->hasProtectedVisibility());
+      }
+    }
   }
-  if (!IsTailCall && CLI.CB && CLI.CB->isMustTailCall())
+  if (!IsTailCall && IsMustTail)
     report_fatal_error("failed to perform tail call elimination on a call "
                        "site marked musttail");
 

llvm/lib/Target/Mips/MipsISelLowering.h

@@ -595,10 +595,9 @@ class TargetRegisterClass;
 
     /// isEligibleForTailCallOptimization - Check whether the call is eligible
     /// for tail call optimization.
-    virtual bool
-    isEligibleForTailCallOptimization(const CCState &CCInfo,
-                                      unsigned NextStackOffset,
-                                      const MipsFunctionInfo &FI) const = 0;
+    virtual bool isEligibleForTailCallOptimization(
+        const CCState &CCInfo, unsigned NextStackOffset,
+        const MipsFunctionInfo &FI, bool IsMustTail = false) const = 0;
 
     /// copyByValArg - Copy argument registers which were used to pass a byval
     /// argument to the stack. Create a stack frame object for the byval

llvm/lib/Target/Mips/MipsSEISelLowering.cpp

@@ -1179,9 +1179,9 @@ MipsSETargetLowering::EmitInstrWithCustomInserter(MachineInstr &MI,
 }
 
 bool MipsSETargetLowering::isEligibleForTailCallOptimization(
-    const CCState &CCInfo, unsigned NextStackOffset,
-    const MipsFunctionInfo &FI) const {
-  if (!UseMipsTailCalls)
+    const CCState &CCInfo, unsigned NextStackOffset, const MipsFunctionInfo &FI,
+    bool IsMustTail) const {
+  if (!UseMipsTailCalls && !IsMustTail)
     return false;
 
   // Exception has to be cleared with eret.

llvm/lib/Target/Mips/MipsSEISelLowering.h

@@ -65,7 +65,7 @@ class TargetRegisterClass;
   private:
     bool isEligibleForTailCallOptimization(
         const CCState &CCInfo, unsigned NextStackOffset,
-        const MipsFunctionInfo &FI) const override;
+        const MipsFunctionInfo &FI, bool IsMustTail = false) const override;
 
     void
     getOpndList(SmallVectorImpl<SDValue> &Ops,

llvm/test/CodeGen/Mips/musttail.ll

@@ -0,0 +1,23 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=mips-unknown-linux-gnu < %s | FileCheck %s --check-prefix=MIPS32
+; RUN: llc -mtriple=mips64-unknown-linux-gnu < %s | FileCheck %s --check-prefix=MIPS64
+
+; Test musttail support for MIPS
+
+define dso_local i32 @callee_args(i32 %a, i32 %b, i32 %c) {
+  ret i32 %a;
+}
+
+define i32 @test_musttail_args(i32 %x, i32 %y, i32 %z) {
+; MIPS32-LABEL: test_musttail_args:
+; MIPS32:       # %bb.0:
+; MIPS32-NEXT:    j callee_args
+; MIPS32-NEXT:    nop
+;
+; MIPS64-LABEL: test_musttail_args:
+; MIPS64:       # %bb.0:
+; MIPS64-NEXT:    j callee_args
+; MIPS64-NEXT:    nop
+  %ret = musttail call i32 @callee_args(i32 %x, i32 %y, i32 %z)
+  ret i32 %ret
+}