Enable generating PPC pre-increment (r+imm) instructions by default.

[oota-llvm.git] / lib / Target / PowerPC / README.txt

diff --git a/lib/Target/PowerPC/README.txt b/lib/Target/PowerPC/README.txt
index e49bda0fcd167c530578dfa8dd1a496ab5c97f7c..349cd890d5eeadd1a58a5224c09fd1adf1d85bdf 100644 (file)
--- a/lib/Target/PowerPC/README.txt
+++ b/lib/Target/PowerPC/README.txt
@@ -37,6 +37,31 @@ _f3:
        ori r3, r2, 65535
        blr 
 
+===-------------------------------------------------------------------------===
+
+This code:
+
+unsigned add32carry(unsigned sum, unsigned x) {
+ unsigned z = sum + x;
+ if (sum + x < x)
+     z++;
+ return z;
+}
+
+Should compile to something like:
+
+       addc r3,r3,r4
+       addze r3,r3
+
+instead we get:
+
+       add r3, r4, r3
+       cmplw cr7, r3, r4
+       mfcr r4 ; 1
+       rlwinm r4, r4, 29, 31, 31
+       add r3, r3, r4
+
+Ick.
 
 ===-------------------------------------------------------------------------===
 
@@ -260,8 +285,8 @@ including having this work sanely.
 Fix Darwin FP-In-Integer Registers ABI
 
 Darwin passes doubles in structures in integer registers, which is very very 
-bad.  Add something like a BIT_CONVERT to LLVM, then do an i-p transformation 
-that percolates these things out of functions.
+bad.  Add something like a BITCAST to LLVM, then do an i-p transformation that
+percolates these things out of functions.
 
 Check out how horrible this is:
 http://gcc.gnu.org/ml/gcc/2005-10/msg01036.html
@@ -889,7 +914,7 @@ entry:
 ; recognize a more elaborate tree than a simple SETxx.
 
 define double @test_FNEG_sel(double %A, double %B, double %C) {
-        %D = sub double -0.000000e+00, %A               ; <double> [#uses=1]
+        %D = fsub double -0.000000e+00, %A               ; <double> [#uses=1]
         %Cond = fcmp ugt double %D, -0.000000e+00               ; <i1> [#uses=1]
         %E = select i1 %Cond, double %B, double %C              ; <double> [#uses=1]
         ret double %E