4ab87ffd1e
SCCP can use PredicateInfo to constrain ranges based on assume and branch conditions. Currently, this is only enabled during IPSCCP. This enables it for SCCP as well, which runs after functions have already been simplified, while IPSCCP runs pre-inline. To a large degree, CVP already handles range-based optimizations, but SCCP is more reliable for the cases it can handle. In particular, SCCP works reliably inside loops, which is something that CVP struggles with due to LVI cycles. I have made various optimizations to make PredicateInfo more efficient, but unfortunately this still has significant compile-time cost (around 0.1-0.2%).
75 lines
2.0 KiB
LLVM
75 lines
2.0 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt < %s -passes=sccp -S | FileCheck %s
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; This is a basic correctness check for constant propagation. The add
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; instruction should be eliminated.
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define i32 @test1(i1 %B) {
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; CHECK-LABEL: @test1(
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; CHECK-NEXT: br i1 [[B:%.*]], label [[BB1:%.*]], label [[BB2:%.*]]
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; CHECK: BB1:
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; CHECK-NEXT: br label [[BB3:%.*]]
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; CHECK: BB2:
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; CHECK-NEXT: br label [[BB3]]
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; CHECK: BB3:
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; CHECK-NEXT: [[RET:%.*]] = phi i32 [ 0, [[BB1]] ], [ 1, [[BB2]] ]
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; CHECK-NEXT: ret i32 [[RET]]
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;
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br i1 %B, label %BB1, label %BB2
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BB1: ; preds = %0
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%Val = add i32 0, 0 ; <i32> [#uses=1]
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br label %BB3
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BB2: ; preds = %0
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br label %BB3
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BB3: ; preds = %BB2, %BB1
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%Ret = phi i32 [ %Val, %BB1 ], [ 1, %BB2 ] ; <i32> [#uses=1]
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ret i32 %Ret
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}
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; This is the test case taken from appel's book that illustrates a hard case
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; that SCCP gets right.
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;
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define i32 @test2(i32 %i0, i32 %j0) {
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; CHECK-LABEL: @test2(
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; CHECK-NEXT: BB1:
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; CHECK-NEXT: br label [[BB2:%.*]]
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; CHECK: BB2:
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; CHECK-NEXT: [[K2:%.*]] = phi i32 [ [[K3:%.*]], [[BB7:%.*]] ], [ 0, [[BB1:%.*]] ]
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; CHECK-NEXT: [[KCOND:%.*]] = icmp slt i32 [[K2]], 100
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; CHECK-NEXT: br i1 [[KCOND]], label [[BB3:%.*]], label [[BB4:%.*]]
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; CHECK: BB3:
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; CHECK-NEXT: br label [[BB5:%.*]]
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; CHECK: BB4:
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; CHECK-NEXT: ret i32 1
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; CHECK: BB5:
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; CHECK-NEXT: [[K3]] = add nsw i32 [[K2]], 1
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; CHECK-NEXT: br label [[BB7]]
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; CHECK: BB7:
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; CHECK-NEXT: br label [[BB2]]
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;
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BB1:
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br label %BB2
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BB2:
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%j2 = phi i32 [ %j4, %BB7 ], [ 1, %BB1 ]
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%k2 = phi i32 [ %k4, %BB7 ], [ 0, %BB1 ]
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%kcond = icmp slt i32 %k2, 100
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br i1 %kcond, label %BB3, label %BB4
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BB3:
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%jcond = icmp slt i32 %j2, 20
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br i1 %jcond, label %BB5, label %BB6
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BB4:
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ret i32 %j2
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BB5:
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%k3 = add i32 %k2, 1
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br label %BB7
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BB6:
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%k5 = add i32 %k2, 1
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br label %BB7
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BB7:
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%j4 = phi i32 [ 1, %BB5 ], [ %k2, %BB6 ]
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%k4 = phi i32 [ %k3, %BB5 ], [ %k5, %BB6 ]
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br label %BB2
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}
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