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Fixes SjLj preparation step on iOS #12
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@alexcrichton PR to LLVM is here: http://reviews.llvm.org/D4256 |
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I'd like to wait for a little bit to see what upstream says. |
added 2 commits
June 28, 2014 00:19
This pass is not Rust-specific, in that all of its transformations are intended to be correct for arbitrary LLVM IR, but it targets idioms found in IR generated by `rustc`, e.g. heavy use of `inbounds` GEPs.
Since the NullCheckElimination pass has a similar intent to the CorrelatedValuePropagation pass, I decided to run it right after the both places that the latter runs.
DiamondLovesYou
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Jun 29, 2014
The full string used to be "// =rust-lang#12" for example, which looks too busy. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209443 91177308-0d34-0410-b5e6-96231b3b80d8
Teach the NullCheckElimination pass about recurrences involving inbounds GEPs. This allows the pass to optimize null checks from most uses of single slice and vector iterators. This still isn't sufficient to eliminate null checks from uses of multiple iterators with zip().
This crash was pretty common while compiling Rust for iOS (armv7). Reason - SjLj preparation step was lowering aggregate arguments as ExtractValue + InsertValue. ExtractValue has assertion which checks that there is some data in value, which is not true in case of empty (no fields) structures. Rust uses them quite extensively so this patch uses a 'select true, %val, undef' instruction to lower the argument. Patch by Valerii Hiora. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212922 91177308-0d34-0410-b5e6-96231b3b80d8
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I believe this was covered by #16 |
alexcrichton
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Aug 4, 2015
No functional change because "lsl #12" is actually encoded as 12, but one less bug if someone ever decides to change that for the giggles. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@243536 91177308-0d34-0410-b5e6-96231b3b80d8
alexcrichton
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Feb 9, 2018
…ddress operands Currently the assembler would accept, e.g. `ldr r0, [s0, #12]` and similar. This patch add checks that only general-purpose registers are used in address operands, shifted registers, and shift amounts. Differential revision: https://reviews.llvm.org/D39910 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@321866 91177308-0d34-0410-b5e6-96231b3b80d8
alexcrichton
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Aug 2, 2018
This reverts commit r337504 while I investigate a TSan bot failure that seems related: http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-autoconf/builds/26526 #8 0x000055581f2895d8 (/b/sanitizer-x86_64-linux-autoconf/build/tsan_debug_build/bin/clang-7+0x1eb45d8) #9 0x000055581f294323 llvm::ConstantAggrKeyType<llvm::ConstantArray>::create(llvm::ArrayType*) const /b/sanitizer-x86_64-linux-autoconf/build/llvm/lib/IR/ConstantsContext.h:409:0 #10 0x000055581f294323 llvm::ConstantUniqueMap<llvm::ConstantArray>::create(llvm::ArrayType*, llvm::ConstantAggrKeyType<llvm::ConstantArray>, std::pair<unsigned int, std::pair<llvm::ArrayType*, llvm::ConstantAggrKeyType<llvm::ConstantArray> > >&) /b/sanitizer-x86_64-linux-autoconf/build/llvm/lib/IR/ConstantsContext.h:635:0 #11 0x000055581f294323 llvm::ConstantUniqueMap<llvm::ConstantArray>::getOrCreate(llvm::ArrayType*, llvm::ConstantAggrKeyType<llvm::ConstantArray>) /b/sanitizer-x86_64-linux-autoconf/build/llvm/lib/IR/ConstantsContext.h:654:0 #12 0x000055581f2944cb llvm::ConstantArray::get(llvm::ArrayType*, llvm::ArrayRef<llvm::Constant*>) /b/sanitizer-x86_64-linux-autoconf/build/llvm/lib/IR/Constants.cpp:964:0 #13 0x000055581fa27e19 llvm::SmallVectorBase::size() const /b/sanitizer-x86_64-linux-autoconf/build/llvm/include/llvm/ADT/SmallVector.h:53:0 #14 0x000055581fa27e19 llvm::SmallVectorImpl<llvm::Constant*>::resize(unsigned long) /b/sanitizer-x86_64-linux-autoconf/build/llvm/include/llvm/ADT/SmallVector.h:347:0 #15 0x000055581fa27e19 (anonymous namespace)::EmitArrayConstant(clang::CodeGen::CodeGenModule&, clang::ConstantArrayType const*, llvm::Type*, unsigned int, llvm::SmallVectorImpl<llvm::Constant*>&, llvm::Constant*) /b/sanitizer-x86_64-linux-autoconf/build/llvm/tools/clang/lib/CodeGen/CGExprConstant.cpp:669:0 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@337511 91177308-0d34-0410-b5e6-96231b3b80d8
alexcrichton
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Aug 22, 2018
Summary:
Currently, in line with GCC, when specifying reserved registers like sp or pc on an inline asm() clobber list, we don't always preserve the original value across the statement. And in general, overwriting reserved registers can have surprising results.
For example:
```
extern int bar(int[]);
int foo(int i) {
int a[i]; // VLA
asm volatile(
"mov r7, #1"
:
:
: "r7"
);
return 1 + bar(a);
}
```
Compiled for thumb, this gives:
```
$ clang --target=arm-arm-none-eabi -march=armv7a -c test.c -o - -S -O1 -mthumb
...
foo:
.fnstart
@ %bb.0: @ %entry
.save {r4, r5, r6, r7, lr}
push {r4, r5, r6, r7, lr}
.setfp r7, sp, #12
add r7, sp, #12
.pad #4
sub sp, #4
movs r1, #7
add.w r0, r1, r0, lsl #2
bic r0, r0, #7
sub.w r0, sp, r0
mov sp, r0
@app
mov.w r7, #1
@NO_APP
bl bar
adds r0, #1
sub.w r4, r7, #12
mov sp, r4
pop {r4, r5, r6, r7, pc}
...
```
r7 is used as the frame pointer for thumb targets, and this function needs to restore the SP from the FP because of the variable-length stack allocation a. r7 is clobbered by the inline assembly (and r7 is included in the clobber list), but LLVM does not preserve the value of the frame pointer across the assembly block.
This type of behavior is similar to GCC's and has been discussed on the bugtracker: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=11807 . No consensus seemed to have been reached on the way forward. Clang behavior has briefly been discussed on the CFE mailing (starting here: http://lists.llvm.org/pipermail/cfe-dev/2018-July/058392.html). I've opted for following Eli Friedman's advice to print warnings when there are reserved registers on the clobber list so as not to diverge from GCC behavior for now.
The patch uses MachineRegisterInfo's target-specific knowledge of reserved registers, just before we convert the inline asm string in the AsmPrinter.
If we find a reserved register, we print a warning:
```
repro.c:6:7: warning: inline asm clobber list contains reserved registers: R7 [-Winline-asm]
"mov r7, #1"
^
```
Reviewers: eli.friedman, olista01, javed.absar, efriedma
Reviewed By: efriedma
Subscribers: efriedma, eraman, kristof.beyls, llvm-commits
Differential Revision: https://reviews.llvm.org/D49727
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@339257 91177308-0d34-0410-b5e6-96231b3b80d8
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Rebased on current used head.