Fix the "test" optimization to recognize "dec" as an add of
negative one, as subtracts of immediates are canonicalized
to adds.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@66180 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index d56e672..33eee7a 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -5382,13 +5382,19 @@
UE = Op.getNode()->use_end(); UI != UE; ++UI)
if (UI->getOpcode() == ISD::STORE)
goto default_case;
- // An add of one will be selected as an INC.
if (ConstantSDNode *C =
- dyn_cast<ConstantSDNode>(Op.getNode()->getOperand(1)))
+ dyn_cast<ConstantSDNode>(Op.getNode()->getOperand(1))) {
+ // An add of one will be selected as an INC.
if (C->getAPIntValue() == 1) {
Opcode = X86ISD::INC;
break;
}
+ // An add of negative one (subtract of one) will be selected as a DEC.
+ if (C->getAPIntValue().isAllOnesValue()) {
+ Opcode = X86ISD::DEC;
+ break;
+ }
+ }
// Otherwise use a regular EFLAGS-setting add.
Opcode = X86ISD::ADD;
break;
@@ -5399,13 +5405,6 @@
UE = Op.getNode()->use_end(); UI != UE; ++UI)
if (UI->getOpcode() == ISD::STORE)
goto default_case;
- // A subtract of one will be selected as a DEC.
- if (ConstantSDNode *C =
- dyn_cast<ConstantSDNode>(Op.getNode()->getOperand(1)))
- if (C->getAPIntValue() == 1) {
- Opcode = X86ISD::DEC;
- break;
- }
// Otherwise use a regular EFLAGS-setting sub.
Opcode = X86ISD::SUB;
break;
diff --git a/test/CodeGen/X86/peep-test.ll b/test/CodeGen/X86/peep-test-0.ll
similarity index 100%
rename from test/CodeGen/X86/peep-test.ll
rename to test/CodeGen/X86/peep-test-0.ll
diff --git a/test/CodeGen/X86/peep-test-1.ll b/test/CodeGen/X86/peep-test-1.ll
new file mode 100644
index 0000000..b4698e3
--- /dev/null
+++ b/test/CodeGen/X86/peep-test-1.ll
@@ -0,0 +1,23 @@
+; RUN: llvm-as < %s | llc -march=x86 > %t
+; RUN: grep dec %t | count 1
+; RUN: not grep test %t
+; RUN: not grep cmp %t
+
+define void @foo(i32 %n, double* nocapture %p) nounwind {
+ br label %bb
+
+bb:
+ %indvar = phi i32 [ 0, %0 ], [ %indvar.next, %bb ]
+ %i.03 = sub i32 %n, %indvar
+ %1 = getelementptr double* %p, i32 %i.03
+ %2 = load double* %1, align 4
+ %3 = mul double %2, 2.930000e+00
+ store double %3, double* %1, align 4
+ %4 = add i32 %i.03, -1
+ %phitmp = icmp slt i32 %4, 0
+ %indvar.next = add i32 %indvar, 1
+ br i1 %phitmp, label %bb, label %return
+
+return:
+ ret void
+}