This is the CodeGen equivalent of r153747. I tested that there is not noticeable
performance difference with any combination of -O0/-O2 /-g when compiling
gcc as a single compilation unit.
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here but it has no other uses, then we have a problem. E.g.,
int foo (const int *x) {
char a[*x];
return 0;
}
If we assign 'a' a vreg and fast isel later on has to use the selection
DAG isel, it will want to copy the value to the vreg. However, there are
no uses, which goes counter to what selection DAG isel expects.
<rdar://problem/11134152>
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Some targets still mess up the liveness information, but that isn't
verified after MRI->invalidateLiveness().
The verifier can still check other useful things like register classes
and CFG, so it should be enabled after all passes.
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The late scheduler depends on accurate liveness information if it is
breaking anti-dependencies, so we should be able to verify it.
Relax the terminator checking in the machine code verifier so it can
handle the basic blocks created by if conversion.
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Extract the liveness verification into its own method.
This makes it possible to run the machine code verifier after liveness
information is no longer required to be valid.
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Branch folding can use a register scavenger to update liveness
information when required. Don't do that if liveness information is
already invalid.
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Late optimization passes like branch folding and tail duplication can
transform the machine code in a way that makes it expensive to keep the
register liveness information up to date. There is a fuzzy line between
register allocation and late scheduling where the liveness information
degrades.
The MRI::tracksLiveness() flag makes the line clear: While true,
liveness information is accurate, and can be used for register
scavenging. Once the flag is false, liveness information is not
accurate, and can only be used as a hint.
Late passes generally don't need the liveness information, but they will
sometimes use the register scavenger to help update it. The scavenger
enforces strict correctness, and we have to spend a lot of code to
update register liveness that may never be used.
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copies being considered for removal. Make sure to track all of the copies,
rather than just the most recent encountered, by holding a DenseSet instead of
an unsigned in SrcMap.
No test case - couldn't reduce something with a sane size.
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backtrace locations.
Testcase forthcoming, but I wanted to get some testing here.
Should fix:
PR12323
PR12314
rdar://11091100
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execution-time regression for nsieve-bits on the ARMv7 -O0 -g nightly tester.
This may also improve compile-time on architectures that would otherwise
generate a libcall for urem (e.g., ARM) or fall back to the DAG selector.
rdar://10810716
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Type legalization can zero-extend the elements of the build_vector node, so,
for example, we may have an <8 x i8> with i32 elements of value 255. That
should return 'true' for the vector being all ones.
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i128). In that case, we may not be able to print out the MCExpr as an
expression. For instance, we could have an MCExpr like this:
0xBEEF0000BEEF0000 | (0xBEEF0000BEEF0000 << 64)
The MCExpr printer handles sizes up to 64-bits, but this expression would
require 128-bits. In this situation, try to evaluate the constant expression and
emit that as the value into 64-bit chunks.
<rdar://problem/11070338>
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a variable. The previous code would break the debug info changing
code invariant. This will regress debug info for arguments where
we elide the alloca created.
Fixes rdar://11066468
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instructions have been scheduled. Handy for tracking down scheduler bugs, or
bugs exposed by scheduling.
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