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authorChris Lattner <sabre@nondot.org>2005-04-07 19:43:53 +0000
committerChris Lattner <sabre@nondot.org>2005-04-07 19:43:53 +0000
commit5a6bace3ab8db44e5412a773626fbb76fb316767 (patch)
tree4557605c8f9d431218e819d3e2ee8268ffc340f9 /lib/CodeGen
parentcbd06fc3d7511d8dcb64386ffa446f1b20b30ae6 (diff)
If a target zero or sign extends the result of its setcc, allow folding of
this into sign/zero extension instructions later. On PPC, for example, this testcase: %G = external global sbyte implementation void %test(int %X, int %Y) { %C = setlt int %X, %Y %D = cast bool %C to sbyte store sbyte %D, sbyte* %G ret void } Now codegens to: cmpw cr0, r3, r4 li r3, 1 li r4, 0 blt .LBB_test_2 ; .LBB_test_1: ; or r3, r4, r4 .LBB_test_2: ; addis r2, r2, ha16(L_G$non_lazy_ptr-"L00000$pb") lwz r2, lo16(L_G$non_lazy_ptr-"L00000$pb")(r2) stb r3, 0(r2) instead of: cmpw cr0, r3, r4 li r3, 1 li r4, 0 blt .LBB_test_2 ; .LBB_test_1: ; or r3, r4, r4 .LBB_test_2: ; *** rlwinm r3, r3, 0, 31, 31 addis r2, r2, ha16(L_G$non_lazy_ptr-"L00000$pb") lwz r2, lo16(L_G$non_lazy_ptr-"L00000$pb")(r2) stb r3, 0(r2) git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@21148 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/CodeGen')
-rw-r--r--lib/CodeGen/SelectionDAG/SelectionDAG.cpp14
1 files changed, 13 insertions, 1 deletions
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 7faf19fd72f..04ccc77b6bb 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -585,7 +585,7 @@ SDOperand SelectionDAG::getNode(unsigned Opcode, MVT::ValueType VT,
break;
case ISD::ZERO_EXTEND:
if (Operand.getValueType() == VT) return Operand; // noop extension
- if (OpOpcode == ISD::ZERO_EXTEND)
+ if (OpOpcode == ISD::ZERO_EXTEND) // (zext (zext x)) -> (zext x)
return getNode(ISD::ZERO_EXTEND, VT, Operand.Val->getOperand(0));
break;
case ISD::TRUNCATE:
@@ -1025,6 +1025,18 @@ SDOperand SelectionDAG::getNode(unsigned Opcode, MVT::ValueType VT,SDOperand N1,
return N1;
}
+ // If we are extending the result of a setcc, and we already know the
+ // contents of the top bits, eliminate the extension.
+ if (N1.getOpcode() == ISD::SETCC)
+ switch (TLI.getSetCCResultContents()) {
+ case TargetLowering::UndefinedSetCCResult: break;
+ case TargetLowering::ZeroOrOneSetCCResult:
+ if (Opcode == ISD::ZERO_EXTEND_INREG) return N1;
+ break;
+ case TargetLowering::ZeroOrNegativeOneSetCCResult:
+ if (Opcode == ISD::SIGN_EXTEND_INREG) return N1;
+ break;
+ }
break;
}