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[ARM] Fix a bug in constant island pass that was triggering an assertion.

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The assert was being triggered when the distance between a constant pool entry
and its user exceeded the maximally allowed distance after thumb2 branch
shortening. A padding was inserted after a thumb2 branch instruction was shrunk,
which caused the user to be out of range. This is wrong as the padding should
have been inserted by the layout algorithm so that the distance between two
instructions doesn't grow later during thumb2 instruction optimization.

This commit fixes the code in ARMConstantIslands::createNewWater to call
computeBlockSize and set BasicBlock::Unalign when a branch instruction is
inserted to create new water after a basic block. A non-zero Unalign causes
the worst-case padding to be inserted when adjustBBOffsetsAfter is called to
recompute the basic block offsets.

rdar://problem/19130476

llvm-svn: 225467
This commit is contained in:
Akira Hatanaka 2015-01-08 20:44:50 +00:00
parent b0dfd1b536
commit 71e44f03e9
2 changed files with 43 additions and 1 deletions
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2
lib/Target/ARM/ARMConstantIslandPass.cpp
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@ -1270,7 +1270,7 @@ void ARMConstantIslands::createNewWater(unsigned CPUserIndex,
unsigned MaxDisp = getUnconditionalBrDisp(UncondBr);
ImmBranches.push_back(ImmBranch(&UserMBB->back(),
MaxDisp, false, UncondBr));
BBInfo[UserMBB->getNumber()].Size += Delta;
computeBlockSize(UserMBB);
adjustBBOffsetsAfter(UserMBB);
return;
}

42
test/CodeGen/Thumb2/constant-islands-new-island-padding.ll Normal file
View File

@ -0,0 +1,42 @@
; RUN: llc < %s -mtriple=thumbv7-apple-ios %s -o - | FileCheck %s
@g0 = common global i32 0, align 4
@d0 = common global double 0.000000e+00, align 8
@f0 = common global float 0.000000e+00, align 4
@g1 = common global i32 0, align 4
declare i32 @llvm.arm.space(i32, i32)
; Check that the constant island pass moves the float constant pool entry inside
; the function.
; CHECK: .long 1067320814 @ float 1.23455596
; CHECK: {{.*}} %do.end
define i32 @testpadding(i32 %a) {
entry:
%0 = load i32* @g0, align 4
%add = add nsw i32 %0, 12
store i32 %add, i32* @g0, align 4
%1 = load double* @d0, align 8
%add1 = fadd double %1, 0x3FF3C0B8ED46EACB
store double %add1, double* @d0, align 8
%tmpcall11 = call i32 @llvm.arm.space(i32 28, i32 undef)
call void @foo20(i32 191)
%2 = load float* @f0, align 4
%add2 = fadd float %2, 0x3FF3C0BDC0000000
store float %add2, float* @f0, align 4
br label %do.body
do.body: ; preds = %do.body, %entry
tail call void @foo20(i32 19)
%3 = load i32* @g1, align 4
%tobool = icmp eq i32 %3, 0
br i1 %tobool, label %do.end, label %do.body
do.end: ; preds = %do.body
%tmpcall111 = call i32 @llvm.arm.space(i32 954, i32 undef)
ret i32 10
}
declare void @foo20(i32)