[SCCP] Remove forcedconstant, go to overdefined instead
This patch removes forcedconstant to simplify things for the
move to ValueLattice, which includes constant ranges, but no
forced constants.
This patch removes forcedconstant and changes ResolvedUndefsIn
to mark instructions with unknown operands as overdefined. This
means we do not do simplifications based on undef directly in SCCP
any longer, but this seems to hardly come up in practice (see stats
below), presumably because InstCombine & others take care
of most of the relevant folds already.
It is still beneficial to keep ResolvedUndefIn, as it allows us delaying
going to overdefined until we propagated all known information.
I also built MultiSource, SPEC2000 and SPEC2006 and compared
sccp.IPNumInstRemoved and sccp.NumInstRemoved. It looks like the impact
is quite low:
Tests: 244
Same hash: 238 (filtered out)
Remaining: 6
Metric: sccp.IPNumInstRemoved
Program base patch diff
test-suite...arks/VersaBench/dbms/dbms.test 4.00 3.00 -25.0%
test-suite...TimberWolfMC/timberwolfmc.test 38.00 34.00 -10.5%
test-suite...006/453.povray/453.povray.test 158.00 155.00 -1.9%
test-suite.../CINT2000/176.gcc/176.gcc.test 668.00 668.00 0.0%
test-suite.../CINT2006/403.gcc/403.gcc.test 1209.00 1209.00 0.0%
test-suite...arks/mafft/pairlocalalign.test 76.00 76.00 0.0%
Tests: 244
Same hash: 238 (filtered out)
Remaining: 6
Metric: sccp.NumInstRemoved
Program base patch diff
test-suite...arks/mafft/pairlocalalign.test 185.00 175.00 -5.4%
test-suite.../CINT2006/403.gcc/403.gcc.test 2059.00 2056.00 -0.1%
test-suite.../CINT2000/176.gcc/176.gcc.test 2358.00 2357.00 -0.0%
test-suite...006/453.povray/453.povray.test 317.00 317.00 0.0%
test-suite...TimberWolfMC/timberwolfmc.test 12.00 12.00 0.0%
Reviewers: davide, efriedma, mssimpso
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D61314
diff --git a/llvm/test/Transforms/SCCP/logical-nuke.ll b/llvm/test/Transforms/SCCP/logical-nuke.ll
index 6ca16de4..5152e12 100644
--- a/llvm/test/Transforms/SCCP/logical-nuke.ll
+++ b/llvm/test/Transforms/SCCP/logical-nuke.ll
@@ -1,39 +1,47 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -sccp -S | FileCheck %s
; Test that SCCP has basic knowledge of when and/or/mul nuke overdefined values.
-; CHECK-LABEL: test
-; CHECK: ret i32 0
define i32 @test(i32 %X) {
+; CHECK-LABEL: @test(
+; CHECK-NEXT: ret i32 0
+;
%Y = and i32 %X, 0
ret i32 %Y
}
-; CHECK-LABEL: test2
-; CHECK: ret i32 -1
define i32 @test2(i32 %X) {
+; CHECK-LABEL: @test2(
+; CHECK-NEXT: ret i32 -1
+;
%Y = or i32 -1, %X
ret i32 %Y
}
-; CHECK-LABEL: test3
-; CHECK: ret i32 0
define i32 @test3(i32 %X) {
+; CHECK-LABEL: @test3(
+; CHECK-NEXT: [[Y:%.*]] = and i32 undef, [[X:%.*]]
+; CHECK-NEXT: ret i32 [[Y]]
+;
%Y = and i32 undef, %X
ret i32 %Y
}
-; CHECK-LABEL: test4
-; CHECK: ret i32 -1
define i32 @test4(i32 %X) {
+; CHECK-LABEL: @test4(
+; CHECK-NEXT: [[Y:%.*]] = or i32 [[X:%.*]], undef
+; CHECK-NEXT: ret i32 [[Y]]
+;
%Y = or i32 %X, undef
ret i32 %Y
}
; X * 0 = 0 even if X is overdefined.
-; CHECK-LABEL: test5
-; CHECK: ret i32 0
define i32 @test5(i32 %foo) {
+; CHECK-LABEL: @test5(
+; CHECK-NEXT: ret i32 0
+;
%patatino = mul i32 %foo, 0
ret i32 %patatino
}