[PATCH] D91020: [X86] Unbind the ebx with GOT address in regcall calling convention

[Xiang Zhang via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rGf2e292446334: [X86] Unbind the ebx with GOT address in regcall calling convention (authored by xiangzhangllvm).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D91020/new/

https://reviews.llvm.org/D91020

Files:
  llvm/lib/Target/X86/X86ISelLowering.cpp
  llvm/test/CodeGen/X86/tailregccpic.ll
  llvm/test/CodeGen/X86/x86-regcall-got.ll


Index: llvm/test/CodeGen/X86/x86-regcall-got.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/X86/x86-regcall-got.ll
@@ -0,0 +1,37 @@
+; RUN: llc -O0 -mtriple=i386-unknown-linux-gnu -relocation-model=pic < %s | FileCheck %s
+
+; Unbind the ebx with GOT address in regcall calling convention, or the following
+; case will failed in register allocation by no register can be used.
+
+;#define REGCALL __attribute__((regcall))
+;int REGCALL func (int i1, int i2, int i3, int i4, int i5);
+;int (REGCALL *fptr) (int, int, int, int, int) = func;
+;int test() {
+;    return fptr(1,2,3,4,5);
+;}
+
+ at fptr = global i32 (i32, i32, i32, i32, i32)* @__regcall3__func, align 4
+
+declare x86_regcallcc i32 @__regcall3__func(i32 inreg, i32 inreg, i32 inreg, i32 inreg, i32 inreg)
+
+; Function Attrs: noinline nounwind optnone
+define i32 @test() {
+; CHECK-LABEL: test:
+; CHECK:       .L0$pb:
+; CHECK-NEXT:    popl %eax
+; CHECK:       .Ltmp0:
+; CHECK-NEXT:    addl    $_GLOBAL_OFFSET_TABLE_+(.Ltmp0-.L0$pb), %eax
+; CHECK-NEXT:    movl    fptr at GOT(%eax), %eax
+; CHECK-NEXT:    movl    (%eax), %ebx
+; CHECK-NEXT:    movl    $1, %eax
+; CHECK-NEXT:    movl    $2, %ecx
+; CHECK-NEXT:    movl    $3, %edx
+; CHECK-NEXT:    movl    $4, %edi
+; CHECK-NEXT:    movl    $5, %esi
+; CHECK-NEXT:    calll   *%ebx
+
+entry:
+  %0 = load i32 (i32, i32, i32, i32, i32)*, i32 (i32, i32, i32, i32, i32)** @fptr, align 4
+  %call = call x86_regcallcc i32 %0(i32 inreg 1, i32 inreg 2, i32 inreg 3, i32 inreg 4, i32 inreg 5)
+  ret i32 %call
+}
Index: llvm/test/CodeGen/X86/tailregccpic.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/X86/tailregccpic.ll
@@ -0,0 +1,26 @@
+; RUN: llc < %s  -mtriple=i386-pc-unknown-linux-gnu -relocation-model=pic | FileCheck %s
+
+ at a0 = global i32 0, align 4
+
+define x86_regcallcc void @tail_call_regcall(i32 %a) nounwind {
+  tail call x86_regcallcc void @__regcall3__func(i32 %a) nounwind
+  ret void
+}
+
+define internal x86_regcallcc void @__regcall3__func(i32 %i1) {
+entry:
+  store i32 %i1, i32* @a0, align 4
+  ret void
+}
+
+;CHECK-LABLE: tail_call_regcall:
+;CHECK:       # %bb.0:
+;CHECK-NEXT:  jmp     __regcall3__func                # TAILCALL
+;CHECK-NEXT:  .Lfunc_end0:
+
+;CHECK-LABLE: __regcall3__func:
+;CHECK:       addl    $_GLOBAL_OFFSET_TABLE_+({{.*}}), %ecx
+;CHECK-NEXT:  movl    a0 at GOT(%ecx), %ecx
+;CHECK-NEXT:  movl    %eax, (%ecx)
+;CHECK-NEXT:  retl
+;CHECK-NEXT:  .Lfunc_end1:
Index: llvm/lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- llvm/lib/Target/X86/X86ISelLowering.cpp
+++ llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -4127,9 +4127,13 @@
 
   if (Subtarget.isPICStyleGOT()) {
     // ELF / PIC requires GOT in the EBX register before function calls via PLT
-    // GOT pointer.
+    // GOT pointer (except regcall).
     if (!isTailCall) {
-      RegsToPass.push_back(std::make_pair(
+      // Indirect call with RegCall calling convertion may use up all the
+      // general registers, so it is not suitable to bind EBX reister for
+      // GOT address, just let register allocator handle it.
+      if (CallConv != CallingConv::X86_RegCall)
+        RegsToPass.push_back(std::make_pair(
           Register(X86::EBX), DAG.getNode(X86ISD::GlobalBaseReg, SDLoc(),
                                           getPointerTy(DAG.getDataLayout()))));
     } else {


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