4698bf145d
This reverts commit41784bed01. Since the original revisionead815924e, 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
44 lines
988 B
LLVM
44 lines
988 B
LLVM
; RUN: opt < %s -jump-threading -S -verify | FileCheck %s
|
|
|
|
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
|
|
target triple = "x86_64-unknown-linux-gnu"
|
|
|
|
; Verify that we do *not* thread any edge. We used to evaluate
|
|
; constant expressions like:
|
|
;
|
|
; icmp ugt i8* null, inttoptr (i64 4 to i8*)
|
|
;
|
|
; as "true", causing jump threading to a wrong destination.
|
|
define void @foo(i8* %arg1, i8* %arg2) {
|
|
; CHECK-LABEL: @foo
|
|
; CHECK-NOT: bb_{{[^ ]*}}.thread:
|
|
entry:
|
|
%cmp1 = icmp eq i8* %arg1, null
|
|
br i1 %cmp1, label %bb_bar1, label %bb_end
|
|
|
|
bb_bar1:
|
|
call void @bar(i32 1)
|
|
br label %bb_end
|
|
|
|
bb_end:
|
|
%cmp2 = icmp ne i8* %arg2, null
|
|
br i1 %cmp2, label %bb_cont, label %bb_bar2
|
|
|
|
bb_bar2:
|
|
call void @bar(i32 2)
|
|
br label %bb_exit
|
|
|
|
bb_cont:
|
|
%cmp3 = icmp ule i8* %arg1, inttoptr (i64 4 to i8*)
|
|
br i1 %cmp3, label %bb_exit, label %bb_bar3
|
|
|
|
bb_bar3:
|
|
call void @bar(i32 3)
|
|
br label %bb_exit
|
|
|
|
bb_exit:
|
|
ret void
|
|
}
|
|
|
|
declare void @bar(i32)
|