llvm-project/llvm/test/Transforms/JumpThreading/thread-two-bbs3.ll

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Resubmit^2: [JumpThreading] Thread jumps through two basic blocks 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
2020-02-06 00:24:01 +08:00
; RUN: opt < %s -jump-threading -S -verify | FileCheck %s
target datalayout = "e-m:w-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-pc-windows-msvc19.16.27026"
; Verify that we do *not* thread any edge. On Windows, we used to
; improperly duplicate EH pads like bb_cleanup below, resulting in an
; assertion failure later down the pass pipeline.
define void @foo([2 x i8]* %0) personality i8* bitcast (i32 ()* @baz to i8*) {
; CHECK-LABEL: @foo
; CHECK-NOT: bb_{{[^ ]*}}.thread:
entry:
invoke void @bar()
to label %bb_invoke unwind label %bb_cleanuppad
bb_invoke:
invoke void @bar()
to label %bb_exit unwind label %bb_cleanuppad
bb_cleanuppad:
%index = phi i64 [ 1, %bb_invoke ], [ 0, %entry ]
%cond1 = phi i1 [ false, %bb_invoke ], [ true, %entry ]
%1 = cleanuppad within none []
br i1 %cond1, label %bb_action, label %bb_cleanupret
bb_action:
%cond2 = icmp eq i64 %index, 0
br i1 %cond2, label %bb_cleanupret, label %bb_exit
bb_exit:
call void @bar()
ret void
bb_cleanupret:
cleanupret from %1 unwind to caller
}
declare void @bar()
declare i32 @baz()