[X86] Fix Windows i1 zeroext conventions to use i8 instead of i32

Summary:
Re-lands r328386 and r328443, reverting r328482.

Incorporates fixes from @mstorsjo in D44876 (thanks!) so that small
parameters in i8 and i16 do not end up in the SysV register parameters
(EDI, ESI, etc).

I added tests for how we receive small parameters, since that is the
important part. It's always safe to store more bytes than will be read,
but the assumptions you make when loading them are what really matter.

I also tested this by self-hosting clang and it passed tests on win64.

Reviewers: mstorsjo, hans

Subscribers: hiraditya, mstorsjo, llvm-commits

Differential Revision: https://reviews.llvm.org/D44900

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@328570 91177308-0d34-0410-b5e6-96231b3b80d8

Author: rnk

lib/Target/X86/X86CallingConv.td

@@ -586,8 +586,8 @@ def CC_X86_Win64_C : CallingConv<[
   // FIXME: Handle byval stuff.
   // FIXME: Handle varargs.
 
-  // Promote i1/i8/i16/v1i1 arguments to i32.
-  CCIfType<[i1, i8, i16, v1i1], CCPromoteToType<i32>>,
+  // Promote i1/v1i1 arguments to i8.
+  CCIfType<[i1, v1i1], CCPromoteToType<i8>>,
 
   // The 'nest' parameter, if any, is passed in R10.
   CCIfNest<CCAssignToReg<[R10]>>,
@@ -609,6 +609,10 @@ def CC_X86_Win64_C : CallingConv<[
   CCIfType<[x86mmx], CCBitConvertToType<i64>>,
 
   // The first 4 integer arguments are passed in integer registers.
+  CCIfType<[i8 ], CCAssignToRegWithShadow<[CL  , DL  , R8B , R9B ],
+                                          [XMM0, XMM1, XMM2, XMM3]>>,
+  CCIfType<[i16], CCAssignToRegWithShadow<[CX  , DX  , R8W , R9W ],
+                                          [XMM0, XMM1, XMM2, XMM3]>>,
   CCIfType<[i32], CCAssignToRegWithShadow<[ECX , EDX , R8D , R9D ],
                                           [XMM0, XMM1, XMM2, XMM3]>>,
 
@@ -628,7 +632,7 @@ def CC_X86_Win64_C : CallingConv<[
 
   // Integer/FP values get stored in stack slots that are 8 bytes in size and
   // 8-byte aligned if there are no more registers to hold them.
-  CCIfType<[i32, i64, f32, f64], CCAssignToStack<8, 8>>,
+  CCIfType<[i8, i16, i32, i64, f32, f64], CCAssignToStack<8, 8>>,
 
   // Long doubles get stack slots whose size and alignment depends on the
   // subtarget.
@@ -841,13 +845,15 @@ def CC_X86_32_MCU : CallingConv<[
 ]>;
 
 def CC_X86_32_FastCall : CallingConv<[
-  // Promote i1/i8/i16/v1i1 arguments to i32.
-  CCIfType<[i1, i8, i16, v1i1], CCPromoteToType<i32>>,
+  // Promote i1 to i8.
+  CCIfType<[i1], CCPromoteToType<i8>>,
 
   // The 'nest' parameter, if any, is passed in EAX.
   CCIfNest<CCAssignToReg<[EAX]>>,
 
   // The first 2 integer arguments are passed in ECX/EDX
+  CCIfInReg<CCIfType<[ i8], CCAssignToReg<[ CL,  DL]>>>,
+  CCIfInReg<CCIfType<[i16], CCAssignToReg<[ CX,  DX]>>>,
   CCIfInReg<CCIfType<[i32], CCAssignToReg<[ECX, EDX]>>>,
 
   // Otherwise, same as everything else.

lib/Target/X86/X86ISelLowering.cpp

@@ -2993,7 +2993,11 @@ SDValue X86TargetLowering::LowerFormalArguments(
             getv64i1Argument(VA, ArgLocs[++I], Chain, DAG, dl, Subtarget);
       } else {
         const TargetRegisterClass *RC;
-        if (RegVT == MVT::i32)
+        if (RegVT == MVT::i8)
+          RC = &X86::GR8RegClass;
+        else if (RegVT == MVT::i16)
+          RC = &X86::GR16RegClass;
+        else if (RegVT == MVT::i32)
           RC = &X86::GR32RegClass;
         else if (Is64Bit && RegVT == MVT::i64)
           RC = &X86::GR64RegClass;

test/CodeGen/X86/win-smallparams.ll

@@ -0,0 +1,67 @@
+; When we accept small parameters on Windows, make sure we do not assume they
+; are zero or sign extended in memory or in registers.
+
+; RUN: llc < %s -mtriple=x86_64-windows-msvc | FileCheck %s --check-prefix=WIN64
+; RUN: llc < %s -mtriple=x86_64-windows-gnu | FileCheck %s --check-prefix=WIN64
+; RUN: llc < %s -mtriple=i686-windows-msvc | FileCheck %s --check-prefix=WIN32
+; RUN: llc < %s -mtriple=i686-windows-gnu | FileCheck %s --check-prefix=WIN32
+
+define void @call() {
+entry:
+  %rv = call i32 @manyargs(i8 1, i16 2, i8 3, i16 4, i8 5, i16 6)
+  ret void
+}
+
+define i32 @manyargs(i8 %a, i16 %b, i8 %c, i16 %d, i8 %e, i16 %f) {
+entry:
+  %aa = sext i8 %a to i32
+  %bb = sext i16 %b to i32
+  %cc = zext i8 %c to i32
+  %dd = zext i16 %d to i32
+  %ee = zext i8 %e to i32
+  %ff = zext i16 %f to i32
+  %t0 = add i32 %aa, %bb
+  %t1 = add i32 %t0, %cc
+  %t2 = add i32 %t1, %dd
+  %t3 = add i32 %t2, %ee
+  %t4 = add i32 %t3, %ff
+  ret i32 %t4
+}
+
+; WIN64-LABEL: call:
+; WIN64-DAG: movw $6, 40(%rsp)
+; WIN64-DAG: movb $5, 32(%rsp)
+; WIN64-DAG: movb $1, %cl
+; WIN64-DAG: movw $2, %dx
+; WIN64-DAG: movb $3, %r8b
+; WIN64-DAG: movw $4, %r9w
+; WIN64: callq manyargs
+
+; WIN64-LABEL: manyargs:
+; WIN64-DAG: movsbl %cl,
+; WIN64-DAG: movswl %dx,
+; WIN64-DAG: movzbl %r8b,
+; WIN64-DAG: movzwl %r9w,
+; WIN64-DAG: movzbl 40(%rsp),
+; WIN64-DAG: movzwl 48(%rsp),
+; WIN64: retq
+
+
+; WIN32-LABEL: _call:
+; WIN32: pushl $6
+; WIN32: pushl $5
+; WIN32: pushl $4
+; WIN32: pushl $3
+; WIN32: pushl $2
+; WIN32: pushl $1
+; WIN32: calll _manyargs
+
+; WIN32-LABEL: _manyargs:
+; WIN32-DAG: movsbl 4(%esp),
+; WIN32-DAG: movswl 8(%esp),
+; WIN32-DAG: movzbl 12(%esp),
+; WIN32-DAG: movzwl 16(%esp),
+; WIN32-DAG: movzbl 20(%esp),
+; WIN32-DAG: movzwl 24(%esp),
+; WIN32: retl
+

test/CodeGen/X86/win32-bool.ll

@@ -0,0 +1,33 @@
+; RUN: llc < %s -mtriple=i686-windows-msvc | FileCheck %s
+; RUN: llc < %s -mtriple=i686-windows-gnu | FileCheck %s
+
+define x86_fastcallcc i32 @pass_fast_bool(i1 inreg zeroext %b) {
+entry:
+  %cond = select i1 %b, i32 66, i32 0
+  ret i32 %cond
+}
+
+; CHECK-LABEL: @pass_fast_bool@4:
+; CHECK-DAG: testb %cl, %cl
+; CHECK-DAG: movl    $66,
+; CHECK:     retl
+
+define x86_vectorcallcc i32 @pass_vector_bool(i1 inreg zeroext %b) {
+entry:
+  %cond = select i1 %b, i32 66, i32 0
+  ret i32 %cond
+}
+
+; CHECK-LABEL: pass_vector_bool@@4:
+; CHECK-DAG: testb %cl, %cl
+; CHECK-DAG: movl    $66,
+; CHECK:     retl
+
+define zeroext i1 @ret_true() {
+entry:
+  ret i1 true
+}
+
+; CHECK-LABEL: ret_true:
+; CHECK:     movb $1, %al
+; CHECK:     retl

test/CodeGen/X86/win64-bool.ll

@@ -0,0 +1,23 @@
+; RUN: llc < %s -mtriple=x86_64-windows-msvc | FileCheck %s --check-prefix=CHECK
+; RUN: llc < %s -mtriple=x86_64-windows-gnu | FileCheck %s --check-prefix=CHECK
+
+define i32 @pass_bool(i1 zeroext %b) {
+entry:
+  %cond = select i1 %b, i32 66, i32 0
+  ret i32 %cond
+}
+
+; CHECK-LABEL: pass_bool:
+; CHECK-DAG: testb %cl, %cl
+; CHECK-DAG: movl    $66,
+; CHECK:     cmovel {{.*}}, %eax
+; CHECK:     retq
+
+define zeroext i1 @ret_true() {
+entry:
+  ret i1 true
+}
+
+; CHECK-LABEL: ret_true:
+; CHECK:     movb $1, %al
+; CHECK:     retq