decompress: conditionally remove bmi2 from context

Use an helper function, which will just return 0 in case the feature is disabled. Allows constant propagation and removal of dead code.
facebook · Sep 26, 2021 · d70d6c2 · d70d6c2
1 parent 02296ca
commit d70d6c2
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Showing 3 changed files with 21 additions and 10 deletions.
diff --git a/lib/decompress/zstd_decompress.c b/lib/decompress/zstd_decompress.c
@@ -261,7 +261,9 @@ static void ZSTD_initDCtx_internal(ZSTD_DCtx* dctx)
 #endif
     dctx->noForwardProgress = 0;
     dctx->oversizedDuration = 0;
-    dctx->bmi2 = ZSTD_cpuid_bmi2(ZSTD_cpuid());
+#if DYNAMIC_BMI2
+    dctx->bmi2 = ZSTD_cpuid_bmi2(ZSTD_cpuid())
+#endif
     dctx->ddictSet = NULL;
     ZSTD_DCtx_resetParameters(dctx);
 #ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION

diff --git a/lib/decompress/zstd_decompress_block.c b/lib/decompress/zstd_decompress_block.c
@@ -133,11 +133,11 @@ size_t ZSTD_decodeLiteralsBlock(ZSTD_DCtx* dctx,
                     if (singleStream) {
                         hufSuccess = HUF_decompress1X_usingDTable_bmi2(
                             dctx->litBuffer, litSize, istart+lhSize, litCSize,
-                            dctx->HUFptr, dctx->bmi2);
+                            dctx->HUFptr, ZSTD_DCtx_get_bmi2(dctx));
                     } else {
                         hufSuccess = HUF_decompress4X_usingDTable_bmi2(
                             dctx->litBuffer, litSize, istart+lhSize, litCSize,
-                            dctx->HUFptr, dctx->bmi2);
+                            dctx->HUFptr, ZSTD_DCtx_get_bmi2(dctx));
                     }
                 } else {
                     if (singleStream) {
@@ -150,13 +150,13 @@ size_t ZSTD_decodeLiteralsBlock(ZSTD_DCtx* dctx,
                         hufSuccess = HUF_decompress1X1_DCtx_wksp_bmi2(
                             dctx->entropy.hufTable, dctx->litBuffer, litSize,
                             istart+lhSize, litCSize, dctx->workspace,
-                            sizeof(dctx->workspace), dctx->bmi2);
+                            sizeof(dctx->workspace), ZSTD_DCtx_get_bmi2(dctx));
 #endif
                     } else {
                         hufSuccess = HUF_decompress4X_hufOnly_wksp_bmi2(
                             dctx->entropy.hufTable, dctx->litBuffer, litSize,
                             istart+lhSize, litCSize, dctx->workspace,
-                            sizeof(dctx->workspace), dctx->bmi2);
+                            sizeof(dctx->workspace), ZSTD_DCtx_get_bmi2(dctx));
                     }
                 }
 
@@ -620,7 +620,7 @@ size_t ZSTD_decodeSeqHeaders(ZSTD_DCtx* dctx, int* nbSeqPtr,
                                                       LL_defaultDTable, dctx->fseEntropy,
                                                       dctx->ddictIsCold, nbSeq,
                                                       dctx->workspace, sizeof(dctx->workspace),
-                                                      dctx->bmi2);
+                                                      ZSTD_DCtx_get_bmi2(dctx));
             RETURN_ERROR_IF(ZSTD_isError(llhSize), corruption_detected, "ZSTD_buildSeqTable failed");
             ip += llhSize;
         }
@@ -632,7 +632,7 @@ size_t ZSTD_decodeSeqHeaders(ZSTD_DCtx* dctx, int* nbSeqPtr,
                                                       OF_defaultDTable, dctx->fseEntropy,
                                                       dctx->ddictIsCold, nbSeq,
                                                       dctx->workspace, sizeof(dctx->workspace),
-                                                      dctx->bmi2);
+                                                      ZSTD_DCtx_get_bmi2(dctx));
             RETURN_ERROR_IF(ZSTD_isError(ofhSize), corruption_detected, "ZSTD_buildSeqTable failed");
             ip += ofhSize;
         }
@@ -644,7 +644,7 @@ size_t ZSTD_decodeSeqHeaders(ZSTD_DCtx* dctx, int* nbSeqPtr,
                                                       ML_defaultDTable, dctx->fseEntropy,
                                                       dctx->ddictIsCold, nbSeq,
                                                       dctx->workspace, sizeof(dctx->workspace),
-                                                      dctx->bmi2);
+                                                      ZSTD_DCtx_get_bmi2(dctx));
             RETURN_ERROR_IF(ZSTD_isError(mlhSize), corruption_detected, "ZSTD_buildSeqTable failed");
             ip += mlhSize;
         }
@@ -1379,7 +1379,7 @@ ZSTD_decompressSequences(ZSTD_DCtx* dctx, void* dst, size_t maxDstSize,
 {
     DEBUGLOG(5, "ZSTD_decompressSequences");
 #if DYNAMIC_BMI2
-    if (dctx->bmi2) {
+    if (ZSTD_DCtx_get_bmi2(dctx)) {
         return ZSTD_decompressSequences_bmi2(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset, frame);
     }
 #endif
@@ -1403,7 +1403,7 @@ ZSTD_decompressSequencesLong(ZSTD_DCtx* dctx,
 {
     DEBUGLOG(5, "ZSTD_decompressSequencesLong");
 #if DYNAMIC_BMI2
-    if (dctx->bmi2) {
+    if (ZSTD_DCtx_get_bmi2(dctx)) {
         return ZSTD_decompressSequencesLong_bmi2(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset, frame);
     }
 #endif

diff --git a/lib/decompress/zstd_decompress_internal.h b/lib/decompress/zstd_decompress_internal.h
@@ -136,7 +136,9 @@ struct ZSTD_DCtx_s
     size_t litSize;
     size_t rleSize;
     size_t staticSize;
+#if DYNAMIC_BMI2 != 0
     int bmi2;                     /* == 1 if the CPU supports BMI2 and 0 otherwise. CPU support is determined dynamically once per context lifetime. */
+#endif
 
     /* dictionary */
     ZSTD_DDict* ddictLocal;
@@ -185,6 +187,13 @@ struct ZSTD_DCtx_s
 #endif
 };  /* typedef'd to ZSTD_DCtx within "zstd.h" */
 
+MEM_STATIC int ZSTD_DCtx_get_bmi2(const struct ZSTD_DCtx_s *dctx) {
+#if DYNAMIC_BMI2 != 0
+	return dctx->bmi2;
+#else
+	return 0;
+#endif
+}
 
 /*-*******************************************************
  *  Shared internal functions