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-rw-r--r--lib/Target/X86/AsmParser/X86AsmParser.cpp6
-rw-r--r--test/MC/AsmParser/X86/x86_instructions.s8
2 files changed, 12 insertions, 2 deletions
diff --git a/lib/Target/X86/AsmParser/X86AsmParser.cpp b/lib/Target/X86/AsmParser/X86AsmParser.cpp
index c8b25cea30..3ecf273a08 100644
--- a/lib/Target/X86/AsmParser/X86AsmParser.cpp
+++ b/lib/Target/X86/AsmParser/X86AsmParser.cpp
@@ -921,8 +921,10 @@ ParseInstruction(StringRef Name, SMLoc NameLoc,
}
// FIXME: Hack to handle "f{mulp,addp} st(0), $op" the same as
- // "f{mulp,addp} $op", since they commute.
- if ((Name == "fmulp" || Name == "faddp") && Operands.size() == 3 &&
+ // "f{mulp,addp} $op", since they commute. We also allow fdivrp/fsubrp even
+ // though they don't commute, solely because gas does support this.
+ if ((Name=="fmulp" || Name=="faddp" || Name=="fsubrp" || Name=="fdivrp") &&
+ Operands.size() == 3 &&
static_cast<X86Operand*>(Operands[1])->isReg() &&
static_cast<X86Operand*>(Operands[1])->getReg() == X86::ST0) {
delete Operands[1];
diff --git a/test/MC/AsmParser/X86/x86_instructions.s b/test/MC/AsmParser/X86/x86_instructions.s
index d182917d2d..6da446821d 100644
--- a/test/MC/AsmParser/X86/x86_instructions.s
+++ b/test/MC/AsmParser/X86/x86_instructions.s
@@ -466,3 +466,11 @@ movmskpd %xmm6, %rax
movmskpd %xmm6, %eax
// CHECK: movmskpd %xmm6, %eax
// CHECK: encoding: [0x66,0x0f,0x50,0xc6]
+
+// rdar://8491845 - Gas supports commuted forms of non-commutable instructions.
+fdivrp %st(0), %st(1) // CHECK: encoding: [0xde,0xf9]
+fdivrp %st(1), %st(0) // CHECK: encoding: [0xde,0xf9]
+
+fsubrp %ST(0), %ST(1) // CHECK: encoding: [0xde,0xe9]
+fsubrp %ST(1), %ST(0) // CHECK: encoding: [0xde,0xe9]
+