4698bf145d
This reverts commit 41784bed01543315a1d03141e6ddc023fd914c0b.
Since the original revision ead815924e6ebeaf02c31c37ebf7a560b5fdf67b,
this revision fixes three issues:
- This revision fixes the Windows build. My original patch improperly
copied EH pads on Windows. This patch disregards jump threading
opportunities having to do with EH pads.
- This revision fixes jump threading to a wrong destination.
Specifically, my original patch treated any Constant other than 0 as 1
while evaluating the branch condition. This bug led to treating
constant expressions like:
icmp ugt i8* null, inttoptr (i64 4 to i8*)
to "true". This patch fixes the bug by calling isOneValue.
- This revision fixes the cost calculation of two basic blocks being
threaded through. Note that getJumpThreadDuplicationCost returns
"(unsigned)~0" for those basic blocks that cannot be duplicated. If
we sum of two return values from getJumpThreadDuplicationCost, we
could have an unsigned overflow like:
(unsigned)~0 + 5 = 4
and mistakenly determine that it's safe and profitable to proceed
with the jump threading opportunity. The patch fixes the bug by
checking each return value before summing them up.
[JumpThreading] Thread jumps through two basic blocks
Summary:
This patch teaches JumpThreading.cpp to thread through two basic
blocks like:
bb3:
%var = phi i32* [ null, %bb1 ], [ @a, %bb2 ]
%tobool = icmp eq i32 %cond, 0
br i1 %tobool, label %bb4, label ...
bb4:
%cmp = icmp eq i32* %var, null
br i1 %cmp, label bb5, label bb6
by duplicating basic blocks like bb3 above. Once we duplicate bb3 as
bb3.dup and redirect edge bb2->bb3 to bb2->bb3.dup, we have:
bb3:
%var = phi i32* [ @a, %bb2 ]
%tobool = icmp eq i32 %cond, 0
br i1 %tobool, label %bb4, label ...
bb3.dup:
%var = phi i32* [ null, %bb1 ]
%tobool = icmp eq i32 %cond, 0
br i1 %tobool, label %bb4, label ...
bb4:
%cmp = icmp eq i32* %var, null
br i1 %cmp, label bb5, label bb6
Then the existing code in JumpThreading.cpp can thread edge
bb3.dup->bb4 through bb4 and eventually create bb3.dup->bb5.
Reviewers: wmi
Subscribers: hiraditya, jfb, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D70247
63 lines
1.2 KiB
LLVM
63 lines
1.2 KiB
LLVM
; RUN: opt < %s -jump-threading -S -verify | FileCheck %s
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target datalayout = "e-i64:64-i128:128-v16:16-v32:32-n16:32:64"
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target triple = "nvptx64-nvidia-cuda"
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$wrapped_tid = comdat any
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$foo = comdat any
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define i32 @wrapped_tid() #0 comdat align 32 {
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%1 = call i32 @tid()
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ret i32 %1
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}
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declare void @llvm.nvvm.barrier0() #1
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; We had a bug where we duplicated basic blocks containing convergent
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; functions like @llvm.nvvm.barrier0 below. Verify that we don't do
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; that.
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define void @foo() local_unnamed_addr #2 comdat align 32 {
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; CHECK-LABEL: @foo
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%1 = call i32 @tid()
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%2 = urem i32 %1, 7
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br label %3
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3:
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%4 = icmp eq i32 %1, 0
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br i1 %4, label %5, label %6
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5:
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call void @bar()
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br label %6
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6:
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; CHECK: call void @llvm.nvvm.barrier0()
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; CHECK-NOT: call void @llvm.nvvm.barrier0()
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call void @llvm.nvvm.barrier0()
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%7 = icmp eq i32 %2, 0
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br i1 %7, label %11, label %8
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8:
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%9 = icmp ult i32 %1, 49
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br i1 %9, label %10, label %11
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10:
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call void @llvm.trap()
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unreachable
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11:
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br label %3
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}
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declare i32 @tid() #2
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declare void @bar()
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declare void @llvm.trap() #3
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attributes #1 = { convergent }
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attributes #2 = { readnone }
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attributes #3 = { noreturn }
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attributes #4 = { convergent }
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