[PATCH][LoopStrengthReduce] Don't trim a formula that uses a subset of required registers

[Adam Nemet]

On Apr 28, 2014, at 3:55 PM, Chandler Carruth <chandlerc at google.com> wrote:

> 
> On Fri, Apr 25, 2014 at 1:39 PM, Andrew Trick <atrick at apple.com> wrote:
> Adam,
> 
> This fix looks great to me! Please go ahead and commit.
> 
> Andy, how does this look good? ;]
> 
> --- /dev/null
> +++ b/test/Transforms/LoopStrengthReduce/ARM64/req-regs.c
> @@ -0,0 +1,36 @@
> +// RUN: clang %s -O3 -target arm64-apple-ios -o - -S -mllvm -debug-only=loop-reduce 2>&1| FileCheck %s
> +// REQUIRES: asserts
> +
> +// LSR used to fail here due to a bug in the ReqRegs test.  To complicate
> +// things, this could only be reproduced with clang because the uses would
> +// come out in different order when invoked through llc.
> +
> +// CHECK: The chosen solution requires
> +// CHECK-NOT: No Satisfactory Solution
> 
> This test runs clang, from the users PATH, with -O3, in an LLVM test. This doesn't work *at all*.
> 
> That really doesn't work. Mind reverting until you have a reduced test case? This is blocking us, so I'd like to get it fixed ASAP.

I’ll revert the test case until we investigate but clang does get substituted in test/lit.cfg.  For me the test runs as:

/Users/anemet/proj/org/llvm/build/Debug+Asserts/bin/clang /Users/anemet/proj/org/llvm/test/Transforms/LoopStrengthReduce/ARM64/req-regs.c -O3 -target arm64-apple-ios -o - -S -mllvm -debug-only=loop-reduce 2>&1| /Users/anemet/proj/org/llvm/build/Debug+Asserts/bin/FileCheck /Users/anemet/proj/org/llvm/test/Transforms/LoopStrengthReduce/ARM64/req-regs.c

with:

/org/llvm/build$ which clang
/usr/bin/clang

Adam
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