Mark vastart_save_xmm_regs as changing EFLAGS

The vastart_save_xmm_regs pseudo-instruction expands to a test and a
branch, so it modifies EFLAGS.  Mark it so, or else the scheduler might
place it in the middle of another test+branch.

This fixes a bug exposed by r192750, which turned on the MI Scheduler
for X86.

<rdar://problem/15627766>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197469 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86InstrCompiler.td b/lib/Target/X86/X86InstrCompiler.td
index 7d10b67bfe6dfeba7af1aa775077457fda18f077..11aa80391c24f1e079c70c01c76a6b63b4db43d3 100644 (file)
--- a/lib/Target/X86/X86InstrCompiler.td
+++ b/lib/Target/X86/X86InstrCompiler.td
@@ -72,7 +72,7 @@ def ADJCALLSTACKUP64   : I<0, Pseudo, (outs), (ins i32imm:$amt1, i32imm:$amt2),
 
 
 // x86-64 va_start lowering magic.
-let usesCustomInserter = 1 in {
+let usesCustomInserter = 1, Defs = [EFLAGS] in {
 def VASTART_SAVE_XMM_REGS : I<0, Pseudo,
                               (outs),
                               (ins GR8:$al,

diff --git a/test/CodeGen/X86/vastart-defs-eflags.ll b/test/CodeGen/X86/vastart-defs-eflags.ll
new file mode 100644 (file)
index 0000000..6017753
--- /dev/null
+++ b/test/CodeGen/X86/vastart-defs-eflags.ll
@@ -0,0 +1,23 @@
+; RUN: llc %s -o - | FileCheck %s
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.10.0"
+
+; Check that vastart handling doesn't get between testb and je for the branch.
+define i32 @check_flag(i32 %flags, ...) nounwind {
+entry:
+; CHECK: {{^}} testb $2, %bh
+; CHECK-NOT: test
+; CHECK: {{^}} je
+  %and = and i32 %flags, 512
+  %tobool = icmp eq i32 %and, 0
+  br i1 %tobool, label %if.end, label %if.then
+
+if.then:                                          ; preds = %entry
+  br label %if.end
+
+if.end:                                           ; preds = %entry, %if.then
+  %hasflag = phi i32 [ 1, %if.then ], [ 0, %entry ]
+  ret i32 %hasflag
+}
+