[PATCH] D22115: Teach FastISel about thiscall (and, hence, about callee-pop).

[Nico Weber via llvm-commits]

thakis created this revision.
thakis added reviewers: majnemer, rnk.
thakis added a subscriber: llvm-commits.

Without this, -O0 builds fail to use fast isel on all member functions in 32-bit Windows compiles: Fast ISel walks from back to front, and each ret on a member function uses thiscall.

Even with this patch, fast isel fails to lower thiscall calls, and it never fires in 64-bit Windows compiles, since those currently have an explicit early return too.  Chrome/mac debug builds of the v8_base target get ~6% slower if I disable fast isel there, so it might be worth trying to get it to fire more often in Windows debug builds.

http://reviews.llvm.org/D22115

Files:
  lib/Target/X86/X86FastISel.cpp
  test/CodeGen/X86/fast-isel-x86.ll

Index: test/CodeGen/X86/fast-isel-x86.ll
===================================================================
--- test/CodeGen/X86/fast-isel-x86.ll
+++ test/CodeGen/X86/fast-isel-x86.ll
@@ -18,11 +18,18 @@
   ret void
 }
 
+; This should pop 8 bytes on return.
+; CHECK-LABEL: thiscallfun:
+; CHECK: retl $8
+define x86_thiscallcc void @thiscallfun(i32* %this, i32 %a, i32 %b) nounwind {
+  ret void
+}
+
 ; Properly initialize the pic base.
 ; CHECK-LABEL: test2:
 ; CHECK-NOT: HHH
-; CHECK: call{{.*}}L2$pb
-; CHECK-NEXT: L2$pb:
+; CHECK: call{{.*}}L3$pb
+; CHECK-NEXT: L3$pb:
 ; CHECK-NEXT: pop
 ; CHECK: HHH
 ; CHECK: retl
@@ -75,7 +82,7 @@
 ; SDag-ISel's arg push:
 ; CHECK: movl %esp, [[REGISTER:%[a-z]+]]
 ; CHECK: movl $42, ([[REGISTER]])
-; CHECK: movl L_test5dllimport$non_lazy_ptr-L5$pb(%eax), %eax
+; CHECK: movl L_test5dllimport$non_lazy_ptr-L6$pb(%eax), %eax
 
 }
 declare dllimport i32 @test5dllimport(i32)
Index: lib/Target/X86/X86FastISel.cpp
===================================================================
--- lib/Target/X86/X86FastISel.cpp
+++ lib/Target/X86/X86FastISel.cpp
@@ -1151,14 +1151,15 @@
   if (CC != CallingConv::C &&
       CC != CallingConv::Fast &&
       CC != CallingConv::X86_FastCall &&
+      CC != CallingConv::X86_ThisCall &&
       CC != CallingConv::X86_64_SysV)
     return false;
 
   if (Subtarget->isCallingConvWin64(CC))
     return false;
 
-  // Don't handle popping bytes on return for now.
-  if (X86MFInfo->getBytesToPopOnReturn() != 0)
+  // Don't handle popping bytes if they don't fit the ret's immediate.
+  if (!isUInt<16>(X86MFInfo->getBytesToPopOnReturn()))
     return false;
 
   // fastcc with -tailcallopt is intended to provide a guaranteed
@@ -1261,9 +1262,15 @@
   }
 
   // Now emit the RET.
-  MachineInstrBuilder MIB =
-    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc,
-            TII.get(Subtarget->is64Bit() ? X86::RETQ : X86::RETL));
+  MachineInstrBuilder MIB;
+  if (X86MFInfo->getBytesToPopOnReturn()) {
+    MIB = BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc,
+                  TII.get(Subtarget->is64Bit() ? X86::RETIQ : X86::RETIL))
+              .addImm(X86MFInfo->getBytesToPopOnReturn());
+  } else {
+    MIB = BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc,
+                  TII.get(Subtarget->is64Bit() ? X86::RETQ : X86::RETL));
+  }
   for (unsigned i = 0, e = RetRegs.size(); i != e; ++i)
     MIB.addReg(RetRegs[i], RegState::Implicit);
   return true;


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D22115.63147.patch
Type: text/x-patch
Size: 2461 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20160707/1f1b51c8/attachment.bin>