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| author | Misha Brukman <brukman+llvm@gmail.com> | 2004-07-28 19:16:10 +0000 |
|---|---|---|
| committer | Misha Brukman <brukman+llvm@gmail.com> | 2004-07-28 19:16:10 +0000 |
| commit | 8b88d906a2a5bd4a6824c83ae1ee4f3aae54664d (patch) | |
| tree | 37cac218b53ac52621da3e04f0b8e67be98a4b52 /lib | |
| parent | a0af38c46a665a58c733062955e1cb7f244569f7 (diff) | |
Add notes on bug involving casting ulong -> double, thanks to Nate Begeman.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@15307 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/Target/PowerPC/README.txt | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/lib/Target/PowerPC/README.txt b/lib/Target/PowerPC/README.txt index e11449efdf..d881fc9a24 100644 --- a/lib/Target/PowerPC/README.txt +++ b/lib/Target/PowerPC/README.txt @@ -6,6 +6,23 @@ Current bugs: * large fixed-size allocas not correct, although should be closer to working. Added code in PPCRegisterInfo.cpp to do >16bit subtractions to the stack pointer. +* ulong to double. ahhh, here's the problem: + floatdidf assumes signed longs. so if the high but of a ulong + just happens to be set, you get the wrong sign. The fix for this + is to call cmpdi2 to compare against zero, if so shift right by one, + convert to fp, and multiply by (add to itself). the sequence would + look like: + {r3:r4} holds ulong a; + li r5, 0 + li r6, 0 (set r5:r6 to ulong 0) + call cmpdi2 ==> sets r3 <, =, > 0 + if r3 > 0 + call floatdidf as usual + else + shift right ulong a, 1 (we could use emitShift) + call floatdidf + fadd f1, f1, f1 (fp left shift by 1) +* linking llvmg++ .s files with gcc instead of g++ Codegen improvements needed: * no alias analysis causes us to generate slow code for Shootout/matrix |