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| author | Benjamin Kramer <benny.kra@googlemail.com> | 2011-02-26 22:48:07 +0000 |
|---|---|---|
| committer | Benjamin Kramer <benny.kra@googlemail.com> | 2011-02-26 22:48:07 +0000 |
| commit | 7466678003f38f985d5b2dffd0917643137b11cf (patch) | |
| tree | 8a0315a7b150080615e132dfa9cfc54c82fa42b1 /lib/Target/README.txt | |
| parent | 981b1c4c62054e4e39570a9230c0318f13f9a0a9 (diff) | |
Add some DAGCombines for (adde 0, 0, glue), which are useful to optimize legalized code for large integer arithmetic.
1. Inform users of ADDEs with two 0 operands that it never sets carry
2. Fold other ADDs or ADDCs into the ADDE if possible
It would be neat if we could do the same thing for SETCC+ADD eventually, but we can't do that in target independent code.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126557 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Target/README.txt')
| -rw-r--r-- | lib/Target/README.txt | 37 |
1 files changed, 0 insertions, 37 deletions
diff --git a/lib/Target/README.txt b/lib/Target/README.txt index f85914b61d9..e01df010436 100644 --- a/lib/Target/README.txt +++ b/lib/Target/README.txt @@ -1780,43 +1780,6 @@ case it choses instead to keep the max operation obvious. //===---------------------------------------------------------------------===// -Take the following testcase on x86-64 (similar testcases exist for all targets -with addc/adde): - -define void @a(i64* nocapture %s, i64* nocapture %t, i64 %a, i64 %b, -i64 %c) nounwind { -entry: - %0 = zext i64 %a to i128 ; <i128> [#uses=1] - %1 = zext i64 %b to i128 ; <i128> [#uses=1] - %2 = add i128 %1, %0 ; <i128> [#uses=2] - %3 = zext i64 %c to i128 ; <i128> [#uses=1] - %4 = shl i128 %3, 64 ; <i128> [#uses=1] - %5 = add i128 %4, %2 ; <i128> [#uses=1] - %6 = lshr i128 %5, 64 ; <i128> [#uses=1] - %7 = trunc i128 %6 to i64 ; <i64> [#uses=1] - store i64 %7, i64* %s, align 8 - %8 = trunc i128 %2 to i64 ; <i64> [#uses=1] - store i64 %8, i64* %t, align 8 - ret void -} - -Generated code: - addq %rcx, %rdx - sbbq %rax, %rax - subq %rax, %r8 - movq %r8, (%rdi) - movq %rdx, (%rsi) - ret - -Expected code: - addq %rcx, %rdx - adcq $0, %r8 - movq %r8, (%rdi) - movq %rdx, (%rsi) - ret - -//===---------------------------------------------------------------------===// - Switch lowering generates less than ideal code for the following switch: define void @a(i32 %x) nounwind { entry: |